Motivated by the recent discovery of charge density wave(CDW)order in the magnetic kagomémetal Fe Ge,we study the single-orbital t-N-V_(1)-V_(2)model on the kagomélattice,where N,V_(1),and V_(2)are the onsit...Motivated by the recent discovery of charge density wave(CDW)order in the magnetic kagomémetal Fe Ge,we study the single-orbital t-N-V_(1)-V_(2)model on the kagomélattice,where N,V_(1),and V_(2)are the onsite,nearest neighbor,and next-nearest-neighbor Coulomb interactions,respectively.When the Fermi level lies in the flat band,the instability toward ferromagnetic(FM)order gives rise to a FM half-metal at sufficiently large onsite N.Intriguingly,at band filling n=17/24,the Fermi level crosses the van Hove singularity of the spin-minority bands of the half-metal.We show that,due to the unique geometry and sublattice interference on the kagomélattice at van Hove singularity,the inter-site Coulomb interactions V_(1) and V_(2)drive a real and an imaginary bond-ordered 2a_(0)×2a_(0) CDW instability,respectively.The FM loop current CDW with complex bond orders is a spin-polarized Chern insulator exhibiting the quantum anomalous Hall effect.The bond fluctuations are found to be substantially enhanced compared to the corresponding nonmagnetic kagomémetals at van Hove filling,providing a concrete model realization of the bond-ordered CDWs,including the FM loop current CDW,over the onsite charge density ordered states.When the spins are partially polarized at an intermediate N,we find that the interplay of CDW and magnetism enables the formation of real and complex bond-ordered CDWs,and the CDW transition is accompanied by a substantial enhancement in the ordered magnetic moments.These findings provide physical insights for the emergence of 2a_(0)×2a_(0) CDWs and their interplay with magnetism on the kagomélattice,and capture the essential physics observed experimentally in Fe Ge.展开更多
The interplay between 2a_(0)×2a_(0)charge density wave(CDW),nematicity and superconductivity in AV_(3)Sb_(5)(A=K,Rb,Cs)compounds gives rise to a rich landscape of intriguing physical phenomena.In addition to the ...The interplay between 2a_(0)×2a_(0)charge density wave(CDW),nematicity and superconductivity in AV_(3)Sb_(5)(A=K,Rb,Cs)compounds gives rise to a rich landscape of intriguing physical phenomena.In addition to the 2a_(0)×2a_(0)CDW,a unidirectional 4a_(0)stripe CDW is also observed on the Sb surface of RbV3Sb5and CsV3Sb5.However,reports of stripe-like CDWs in KV3Sb5have been limited.Here,we report the first observation of a long-range unidirectional stripe order with a 6a_(0)modulation period on the Sb surface of KV_(3)Sb_(5),coexisting with the 2a_(0)×2a_(0)CDW.Notably,the intensity of the6a_(0)stripes in STM topographies exhibits pronounced contrast reversal between opposite bias voltages.Additionally,the wave vector of the 6a_(0)modulation shows no energy-dependent dispersion,confirming its CDW origin.Furthermore,the6a_(0)CDW is robust under a 7 T out-of-plane magnetic field and persists over a temperature range from 215 mK to 720 mK.These results provide compelling evidence for the emergence of a long-range unidirectional CDW in KV_(3)Sb_(5).展开更多
The charge density wave(CDW)state is a ubiquitous ordered phase in condensed matter systems,characterized by a periodic modulation of the electronic charge density.In many CDW materials,superconductivity(SC)emerges in...The charge density wave(CDW)state is a ubiquitous ordered phase in condensed matter systems,characterized by a periodic modulation of the electronic charge density.In many CDW materials,superconductivity(SC)emerges in close proximity to,or coexists with,the CDW phase,offering a valuable platform to explore the interplay between these two competing orders.The ZrTe_(3-x)Se_(x)family provides an ideal system for investigating this interplay,as both CDW-dominated and superconductivity-dominated end members have been well studied,while the intermediate compositions remain largely unexplored.In this study,we employ high-resolution angle-resolved photoemission spectroscopy(ARPES)to systematically investigate the band structure and CDW gap in Se-doped ZrTe_(3-x)Se_(x)(x=0.015),a prototypical system exhibiting the coexistence of CDW and superconductivity phases.Detailed analysis of the band structure across the Brillouin zone reveals highly momentum-dependent,anisotropic CDW gaps.Quasi-2D Fermi surface centered at F exhibits the absence of CDW gap,while on quasi-1D Fermi surface along the Brillouin zone boundary,there is also a highly anisotropic distribution of CDW gap.The gap is zero at B,while reaching its maximum at a nesting vector consistent with the bulk CDW modulation.These results provide direct evidence that quasi-1D Fermi surface nesting is the primary driving force behind CDW formation in this compound.Notably,our measurements reveal a strongly suppressed density of state around EFeven out of CDW gap and absence of band folding induced by Fermi surface nesting.This observation suggests that selenium doping enhances fluctuations of the CDW order parameter,thereby weakening the long-range CDW coherence.Such enhanced fluctuations are likely to facilitate SC pairing,contributing to the observed increase in the SC transition temperature of the doped samples.Our findings not only provide comprehensive understanding of the CDW state in the ZrTe_(3-x)Se_(x)family but also demonstrate that chemical doping provides an effective route to tune the competition between CDW and superconductivity.展开更多
Monolayer vanadium ditelluride(VTe_(2))exhibits a 2√3×2√3 charge-density-wave(CDW)order intertwined with a Mott-insulating state.However,the physical mechanisms driving the emergence of the CDW order and the Mo...Monolayer vanadium ditelluride(VTe_(2))exhibits a 2√3×2√3 charge-density-wave(CDW)order intertwined with a Mott-insulating state.However,the physical mechanisms driving the emergence of the CDW order and the Mott-insulating state are still not well understood.In this study,we systematically investigate the electronic band structure,phonon dispersion,and electron-phonon coupling(EPC)of monolayer VTe_(2)under applied biaxial strain.Our results reveal that the 2√3×2√3 CDW phase is metastable in free-standing monolayer VTe_(2)but becomes stabilized under compressive strain below ε=-2%.The formation of the CDW order originates predominantly from strong EPC,rather than from Fermi-surface nesting.The narrowing of the bandwidth due to the CDW order,combined with correlation effects associated with the V3d orbitals,collectively drive the system into a Mott-insulating state.Furthermore,we find that tensile strain suppresses the CDW order and induces a superconducting state above a critical strain threshold(ε=2%).These findings enhance our understanding of correlation physics in monolayer VTe_(2)and provide a pathway for strain-engineered manipulation of quantum phases in two-dimensional transition-metal dichalcogenides.展开更多
The complex symmetry breaking states in AV3Sb5 family have attracted extreme research attention,but controversy still exists,especially in the question of time reversal symmetry breaking of the charge density wave(CDW...The complex symmetry breaking states in AV3Sb5 family have attracted extreme research attention,but controversy still exists,especially in the question of time reversal symmetry breaking of the charge density wave(CDW).Most recently,a chiral CDW has been suggested in kagome magnet FeGe,but the related study is very rare.Here,we use a scanning tunneling microscope to study the symmetry breaking behavior of both the short-and long-range CDWs in FeGe.Different from previous studies,our study reveals an isotropic long-range CDW without obvious symmetry breaking,while local rotational symmetry breaking appears in the short-range CDW,which may be related to the existence of strong structural disorders.Moreover,the charge distribution of the short-range CDW is inert to the applied external magnetic fields and the detailed spin arrangements of FeGe,inconsistent with the expectation of a chiral CDW associated with chiral flux.Our results rule out the existence of spontaneous chiral and rotational symmetry breaking in the CDW state of FeGe,putting strong constraints on the further understanding of CDW mechanism.展开更多
The structural features and three-dimensional nature of the charge density wave （CDW） state of the layered chalcogenide 1T-TaSe2-xTex （0≤x≤2.0） are characterized by Cs-corrected transmission electron microscopy ...The structural features and three-dimensional nature of the charge density wave （CDW） state of the layered chalcogenide 1T-TaSe2-xTex （0≤x≤2.0） are characterized by Cs-corrected transmission electron microscopy measurements. Notable changes of both average structure and the CDW state arising from Te substitution for Se are clearly demonstrated in samples with x〉0.3. The commensurate CDW state characterized by the known star-of-David clustering in the 1T-TaSe2 crystal becomes visibly unstable with Te substitution and vanishes when x=0.3. The 1T-TaSe2-xTex （0.3≤x≤1.3） samples generally adopt a remarkable incommensurate CDW state with monoclinic distortion, which could be fundamentally in correlation with the strong qq-dependent electron-phonon coupling-induced period-lattice-distortion as identified in TaTe22. Systematic analysis demonstrates that the occurrence of superconductivity is related to the suppression of the commensurate CDW phase and the presence of discommensuration is an evident structural feature observed in the superconducting samples.展开更多
Charge density wave(CDW)strongly affects the electronic properties of two-dimensional(2D)materials and can be tuned by phase engineering.Among 2D transitional metal dichalcogenides(TMDs),VTe_(2)was predicted to requir...Charge density wave(CDW)strongly affects the electronic properties of two-dimensional(2D)materials and can be tuned by phase engineering.Among 2D transitional metal dichalcogenides(TMDs),VTe_(2)was predicted to require small energy for its phase transition and shows unexpected CDW states in its T-phase.However,the CDW state of H-VTe_(2)has been barely reported.Here,we investigate the CDW states in monolayer(ML)H-VTe_(2),induced by phase-engineering from T-phase VTe_(2).The phase transition between T-and H-VTe_(2)is revealed with x-ray photoelectron spectroscopy(XPS)and scanning transmission electron microscopy(STEM)measurements.For H-VTe_(2),scanning tunneling microscope(STM)and low-energy electron diffraction(LEED)results show a robust 2√3×2√3CDW superlattice with a transition temperature above 450 K.Our findings provide a promising way for manipulating the CDWs in 2D materials and show great potential in its application of nanoelectronics.展开更多
As a special order of electronic correlation induced by spatial modulation, the charge density wave(CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in...As a special order of electronic correlation induced by spatial modulation, the charge density wave(CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in various temperatures, we discover a hidden incommensurate stripe-like CDW order besides the(■) CDW phase at low-temperature of 4 K in the epitaxial monolayer 1T-VSe_(2) film. Combining the variable-temperature angle-resolved photoemission spectroscopic(ARPES) measurements, we discover a two-step transition of an anisotropic CDW gap structure that consists of two parts △_(1) and△_(2). The gap part ?1 that closes around ~ 150 K is accompanied with the vanish of the(√7×√3) CDW phase. While another momentum-dependent gap part △_(2) can survive up to ~ 340 K, and is suggested to the result of the incommensurate CDW phase. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure △_(1) +△_(2), which suggests different forming mechanisms between the(√7×√3) and the incommensurate CDW phases. Our findings provide significant information and deep understandings on the CDW phases in monolayer 1T-VSe_(2) film as a two-dimensional(2D) material.展开更多
Recently, modifications of charge density wave（CDW） in two-dimensional（2D） show intriguing properties in quasi-2D materials such as layered transition metal dichalcogenides（TMDCs）. Optical, electrical transport ...Recently, modifications of charge density wave（CDW） in two-dimensional（2D） show intriguing properties in quasi-2D materials such as layered transition metal dichalcogenides（TMDCs）. Optical, electrical transport measurements and scanning tunneling microscopy uncover the enormous difference on the many-body states when the thickness is reduced down to monolayer. However, the CDW in quasi-one-dimensional（1D） materials like transition metal trichalcogenides（TMTCs） is yet to be explored in low dimension whose mechanism is likely distinct from their quasi-2D counterparts.Here, we report a systematic study on the CDW properties of titanium trisulfide（TiS3）. Two phase transition temperatures were observed to decrease from 53 K（103 K） to 46 K（85 K） for the bulk and 〈 15-nm thick nanoribbon, respectively,which arises from the increased fluctuation effect across the chain in the nanoribbon structure, thereby destroying the CDW coherence. It also suggests a strong anisotropy of CDW states in quasi-1D TMTCs which is different from that in TMDCs.Remarkably, by using back gate of-30 V ～ 70 V in 15-nm device, we can tune the second transition temperature from110 K（at-30 V） to 93 K（at 70 V） owing to the altered electron concentration. Finally, the optical approach through the impinging of laser beams on the sample surface is exploited to manipulate the CDW transition, where the melting of the CDW states shows a strong dependence on the excitation energy. Our results demonstrate TiS3 as a promising quasi-1D CDW material and open up a new window for the study of collective phases in TMTCs.展开更多
Layered lanthanum silver antimonide LaAgSb_(2)exhibits both charge density wave(CDW)order and Dirac-cone-like band structure at ambient pressure.Here,we systematically investigate the pressure evolution of structural ...Layered lanthanum silver antimonide LaAgSb_(2)exhibits both charge density wave(CDW)order and Dirac-cone-like band structure at ambient pressure.Here,we systematically investigate the pressure evolution of structural and electronic properties of LaAgSb_(2)single crystal.We show that the CDW order is destabilized under compression,as evidenced by the gradual suppression of magnetoresistance.At P_(C)~22 GPa,synchrotron x-ray diffraction and Raman scattering measurements reveal a structural modification at room-temperature.Meanwhile,the sign change of the Hall coefficient is observed at 5 K.Our results demonstrate the tunability of CDW order in the pressurized LaAgSb_(2)single crystal,which can be helpful for its potential applications in the next-generation devices.展开更多
The effect of strain on charge density wave(CDW)order inα-U is investigated within the framework of relativistic density-functional theory.The energetical stability ofα-U with CDW distortion is enhanced by the tensi...The effect of strain on charge density wave(CDW)order inα-U is investigated within the framework of relativistic density-functional theory.The energetical stability ofα-U with CDW distortion is enhanced by the tensile strain along a and b axes,which is similar to the case of negative pressure and normal.However,the tensile strain along c axis suppresses the energetical stability of CDW phase.This abnormal effect could be understood from the emergence of a new onedimensional atomic chain along c axis inα-U.Furthermore,this effect is supported by the calculations of Fermi surface and phonon mode,in which the topological objects and the dynamical instability show opposite behaviors between strains along a/b and c axes.展开更多
Anisotropy is an important feature of layered materials,and a large anisotropy is usually related to the two-dimensional charac teristics.We investigated the anisotropy of the layered transition metal dicalcogenide 2H...Anisotropy is an important feature of layered materials,and a large anisotropy is usually related to the two-dimensional charac teristics.We investigated the anisotropy of the layered transition metal dicalcogenide 2H-NbSe_(2)in the superconducting and charge density wave(CDW)states using magnetotransport measurements.In the superconducting state,the normalized H_(c2)^(‖c)/H_(p)is independent of the thickness of 2H-NbSe_(2),while H_(c2)^(‖ab)/H_p increases significantly with decreasing thickness,where H_p is the Pauli limiting magnetic field and H_(c2)^(‖c)anu H_(c2)^(‖ab)are the upper critical fields in the c and ab directions,respectively.It is found that the superconducting anisotropy parameterγH_(c2)=H_(c2)^(‖ab)/H_(c2)^(‖c)increases with reduction in the thickness of 2H-NbSe_(2).In the CDW state,the angular(θ)dependence of magnetoresistance,R(H,θ)scales with H(cos^(2)θ+γ_(CDW)^(-2)sin^(2)θ)^(1/2),which decreases with increasing temperature and disappears at about 40 K.It is found that the CDW anisotropy parameterγ_(CDW)is much larger than the effective mass anisotropy but does not change a lot for ultrathin and bulk samples.Our results suggest the existence of three-dimensional superconductivity and quasi-two dimensional CDWs in bulk 2H-NbSe_(2).展开更多
Domain walls(DWs)in the charge-density-wave(CDW)Mott insulator 1T-TaS_(2)have unique localized states,which play an important role in exploring the electronic properties of the material.However,the electronic states i...Domain walls(DWs)in the charge-density-wave(CDW)Mott insulator 1T-TaS_(2)have unique localized states,which play an important role in exploring the electronic properties of the material.However,the electronic states in DWs in 1TTaS_(2)have not been clearly understood,mostly due to the complex structures,phases,and interlayer stacking orders in the DW areas.Here,we explored the electronic states of DWs in the large-area CDW phase and mosaic phase of 1T-TaS_(2)by scanning tunneling spectroscopy.Due to the different densities of DWs,the electronic states of DWs show distinct features in these phases.In the large area CDW phase,both the domain and the DWs(DW1,DW2,DW4)have zero conductance at the Fermi level;while in the mosaic phase,they can be metallic or insulating depending on their environments.In areas with a high density of DWs,some electronic states were observed both on the DWs and within the domains,indicating delocalized states over the whole region.Our work contributes to further understanding of the interplay between CDW and electron correlations in 1T-TaS_(2).展开更多
Owing to the unique electronic structure,kagome materials AV_(3)Sb_(5)(A=K,Rb,Cs)provide a fertile platform of quantum phenomena such as the strongly correlated state and topological Dirac band.It is well known that R...Owing to the unique electronic structure,kagome materials AV_(3)Sb_(5)(A=K,Rb,Cs)provide a fertile platform of quantum phenomena such as the strongly correlated state and topological Dirac band.It is well known that RbV_(3)Sb_(5)exhibits a 2×2 unconventional charge density wave(CDW)state at low temperature,and the mechanism is controversial.Here,by using scanning tunneling microscopy/spectroscopy(STM/STS),we successfully manipulated the CDW state in the Sb plane of RbV_(3)Sb_(5),and realized a new3(1/2)×3(1/2)modulation together with the ubiquitous 2×2 period in the CDW state of RbV_(3)Sb_(5).This work provides a new understanding of the collective quantum ground states in the kagome materials.展开更多
Thermodynamic properties of the charge density wave(CDW) transition in potassium blue bronze K 0.3 MoO 3 are investigated by the measurement of specific heat. A second order phase transition is observed at 177...Thermodynamic properties of the charge density wave(CDW) transition in potassium blue bronze K 0.3 MoO 3 are investigated by the measurement of specific heat. A second order phase transition is observed at 177.5 K. The specific heat jump, and enthalpy and entropy changes associated with the transition are estimated. The results suggest that the lattice plays an important role in thermodynamics for this compound. Analysis of the data near CDW transition shows that width of critical region is about 6 K and the critical behavior belongs to the universality class of the three dimensional XY model.展开更多
We investigate the topological phase transition driven by non-local electronic correlations in a realistic quantum anomalous Hall model consisting of d_(xy)–d_(x^(2)-y^(2)) orbitals. Three topologically distinct phas...We investigate the topological phase transition driven by non-local electronic correlations in a realistic quantum anomalous Hall model consisting of d_(xy)–d_(x^(2)-y^(2)) orbitals. Three topologically distinct phases defined in the noninteracting limit evolve to different charge density wave phases under correlations. Two conspicuous conclusions were obtained: The topological phase transition does not involve gap-closing and the dynamical fluctuations significantly suppress the charge order favored by the next nearest neighbor interaction. Our study sheds light on the stability of topological phase under electronic correlations, and we demonstrate a positive role played by dynamical fluctuations that is distinct to all previous studies on correlated topological states.展开更多
The kagome lattice,characterized by its network of cornersharing triangles,provides an excellent platform for studying various novel quantum phenomena.The recently discovered kagome metal AV3Sb5(A=K,Rb,Cs)[1]garners s...The kagome lattice,characterized by its network of cornersharing triangles,provides an excellent platform for studying various novel quantum phenomena.The recently discovered kagome metal AV3Sb5(A=K,Rb,Cs)[1]garners significant attention for its unique properties,including an unconventional charge density wave(CDW)and superconductivity(SC)[2],as well as the interplay between CDW and SC[3].展开更多
The recent discovery of superconductivity in La_(3)Ni_(2)O_(7-δ)with a transition temperature Tc close to 80 K at high pressures has attracted significant attention,due particularly to a possible density wave(DW)tran...The recent discovery of superconductivity in La_(3)Ni_(2)O_(7-δ)with a transition temperature Tc close to 80 K at high pressures has attracted significant attention,due particularly to a possible density wave(DW)transition occurring near the superconducting dome.Identifying the type of DW order is crucial for understanding the origin of superconductivity in this system.However,owing to the presence of La4Ni3O10 and other intergrowth phases in La_(3)Ni_(2)O_(7-δ)samples,extracting the intrinsic information from the La_(3)Ni_(2)O_(7) phase is challenging.In this study,we employed ^(139)La nuclear quadrupole resonance(NQR)measurements to eliminate the influence of other structural phases in the sample and obtain microscopic insights into the DW transition in La_(3)Ni_(2)O_(7-δ).Below the DW transition temperature T_(DW)∼153 K,we observe a distinct splitting in the±5/2↔±7/2 transition of the NQR resonance peak at the La(2)site,while only a line broadening is seen in the±3/2↔±5/2 transition peak.Through further analysis of the spectra,we show that the line splitting is due to a unidirectional charge modulation.A magnetic line broadening is also observed below T_(DW),accompanied by a large enhancement of the spin-lattice relaxation rate,indicating the formation of magnetically ordered moments in the DW state.Our results suggest a simultaneous formation of charge-and spin-density wave orders in La_(3)Ni_(2)O_(7-δ),thereby offering critical insights into the electronic correlations in Ni-based superconductors.展开更多
Recent advances in strain engineering have enabled unprecedented control over quantum states in strongly correlated magnetic systems.However,nanoscale strain modulation of charge density waves(CDWs)and magnetically ex...Recent advances in strain engineering have enabled unprecedented control over quantum states in strongly correlated magnetic systems.However,nanoscale strain modulation of charge density waves(CDWs)and magnetically excited states,which is crucial for atomically precise strain engineering and practical spintronic applications,remains unexplored.Here,we report the nanoscale strain effects on CDWs and low-energy electronic states in the van der Waals antiferromagnetic metal GdTe_(3),utilizing scanning tunneling microscopy/spectroscopy.Lowtemperature cleavage introduces local strains,resulting in the formation of nanoscale wrinkles on the GdTe_(3)surface.Atomic displacement analysis reveals two distinct types of wrinkles:Wrinkle-I,originating from unidirectional strain,and Wrinkle-II,dominated by shear strain.In Wrinkle-I,the tensile strain enhances the CDW gap,while the compressive strain induces a single low-energy magnetic state.Wrinkle-II switches the orientation of CDW,leading to the formation of an associated CDW domain wall.In addition,three low-energy magnetic states that exhibit magnetic field-dependent shifts and intensity variations emerge within the CDW gap around Wrinkle-II,indicative of a strain-tuned coupling between CDW order and localized 4f-electron magnetism.These findings establish nanoscale strain as a powerful tuning knob for manipulating intertwined electronic and magnetic excitations in correlated magnetic systems.展开更多
Charge density wave(CDW) in kagome materials with the geometric frustration is able to carry unconventional characteristics.Recently, a CDW has been observed below the antiferromagnetic order in kagome FeGe, in which ...Charge density wave(CDW) in kagome materials with the geometric frustration is able to carry unconventional characteristics.Recently, a CDW has been observed below the antiferromagnetic order in kagome FeGe, in which magnetism and CDW are intertwined to form an emergent quantum ground state. However, the CDW is only short-ranged and the structural modulation originating from it has yet to be determined experimentally. Here we realize a long-range CDW order by post-annealing process,and resolve the structure model through single crystal X-ray diffraction. Occupational disorder of Ge resulting from short-range CDW correlations above T_(CDW) is identified from structure refinements. The partial dimerization of Ge along the c axis is unveiled to be the dominant distortion for the CDW. Occupational disorder of Ge is also proved to exist in the CDW phase due to the random selection of partially dimerized Ge sites. Our work provides useful insights for understanding the unconventional nature of the CDW in FeGe.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403800 and 2023YFA1407300)the National Natural Science Foundation of China(Grant Nos.12374153,12447101,and 11974362)supported by the U.S.Department of Energy,Basic Energy Sciences(Grant No.DE-FG02-99ER45747)。
文摘Motivated by the recent discovery of charge density wave(CDW)order in the magnetic kagomémetal Fe Ge,we study the single-orbital t-N-V_(1)-V_(2)model on the kagomélattice,where N,V_(1),and V_(2)are the onsite,nearest neighbor,and next-nearest-neighbor Coulomb interactions,respectively.When the Fermi level lies in the flat band,the instability toward ferromagnetic(FM)order gives rise to a FM half-metal at sufficiently large onsite N.Intriguingly,at band filling n=17/24,the Fermi level crosses the van Hove singularity of the spin-minority bands of the half-metal.We show that,due to the unique geometry and sublattice interference on the kagomélattice at van Hove singularity,the inter-site Coulomb interactions V_(1) and V_(2)drive a real and an imaginary bond-ordered 2a_(0)×2a_(0) CDW instability,respectively.The FM loop current CDW with complex bond orders is a spin-polarized Chern insulator exhibiting the quantum anomalous Hall effect.The bond fluctuations are found to be substantially enhanced compared to the corresponding nonmagnetic kagomémetals at van Hove filling,providing a concrete model realization of the bond-ordered CDWs,including the FM loop current CDW,over the onsite charge density ordered states.When the spins are partially polarized at an intermediate N,we find that the interplay of CDW and magnetism enables the formation of real and complex bond-ordered CDWs,and the CDW transition is accompanied by a substantial enhancement in the ordered magnetic moments.These findings provide physical insights for the emergence of 2a_(0)×2a_(0) CDWs and their interplay with magnetism on the kagomélattice,and capture the essential physics observed experimentally in Fe Ge.
基金Project supported by the National Key Research and Development Project of China(Grant Nos.2024YFA1207700 and 2022YFA1204100)the National Natural Science Foundation of China(Grant No.62488201)+2 种基金the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-003)the Youth Innovation Promotion Association(Grant No.2023005)the Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘The interplay between 2a_(0)×2a_(0)charge density wave(CDW),nematicity and superconductivity in AV_(3)Sb_(5)(A=K,Rb,Cs)compounds gives rise to a rich landscape of intriguing physical phenomena.In addition to the 2a_(0)×2a_(0)CDW,a unidirectional 4a_(0)stripe CDW is also observed on the Sb surface of RbV3Sb5and CsV3Sb5.However,reports of stripe-like CDWs in KV3Sb5have been limited.Here,we report the first observation of a long-range unidirectional stripe order with a 6a_(0)modulation period on the Sb surface of KV_(3)Sb_(5),coexisting with the 2a_(0)×2a_(0)CDW.Notably,the intensity of the6a_(0)stripes in STM topographies exhibits pronounced contrast reversal between opposite bias voltages.Additionally,the wave vector of the 6a_(0)modulation shows no energy-dependent dispersion,confirming its CDW origin.Furthermore,the6a_(0)CDW is robust under a 7 T out-of-plane magnetic field and persists over a temperature range from 215 mK to 720 mK.These results provide compelling evidence for the emergence of a long-range unidirectional CDW in KV_(3)Sb_(5).
基金support from the National Key R&D Program of China(Grant No.2023YFA1407400)the National Natural Science Foundation of China(Grant No.12374063)+4 种基金the National Natural Science Foundation of China(GrantNo.12488101)the Shanghai Natural Science Fund for Original Exploration Program(Grant No.23ZR1479900)the Cultivation Project of Shanghai Research Center for Quantum Sciences(Grant No.LZPY2024)support from the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302700)the New Cornerstone Science Foundation(Grant No.23H010801236)。
文摘The charge density wave(CDW)state is a ubiquitous ordered phase in condensed matter systems,characterized by a periodic modulation of the electronic charge density.In many CDW materials,superconductivity(SC)emerges in close proximity to,or coexists with,the CDW phase,offering a valuable platform to explore the interplay between these two competing orders.The ZrTe_(3-x)Se_(x)family provides an ideal system for investigating this interplay,as both CDW-dominated and superconductivity-dominated end members have been well studied,while the intermediate compositions remain largely unexplored.In this study,we employ high-resolution angle-resolved photoemission spectroscopy(ARPES)to systematically investigate the band structure and CDW gap in Se-doped ZrTe_(3-x)Se_(x)(x=0.015),a prototypical system exhibiting the coexistence of CDW and superconductivity phases.Detailed analysis of the band structure across the Brillouin zone reveals highly momentum-dependent,anisotropic CDW gaps.Quasi-2D Fermi surface centered at F exhibits the absence of CDW gap,while on quasi-1D Fermi surface along the Brillouin zone boundary,there is also a highly anisotropic distribution of CDW gap.The gap is zero at B,while reaching its maximum at a nesting vector consistent with the bulk CDW modulation.These results provide direct evidence that quasi-1D Fermi surface nesting is the primary driving force behind CDW formation in this compound.Notably,our measurements reveal a strongly suppressed density of state around EFeven out of CDW gap and absence of band folding induced by Fermi surface nesting.This observation suggests that selenium doping enhances fluctuations of the CDW order parameter,thereby weakening the long-range CDW coherence.Such enhanced fluctuations are likely to facilitate SC pairing,contributing to the observed increase in the SC transition temperature of the doped samples.Our findings not only provide comprehensive understanding of the CDW state in the ZrTe_(3-x)Se_(x)family but also demonstrate that chemical doping provides an effective route to tune the competition between CDW and superconductivity.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1403203)。
文摘Monolayer vanadium ditelluride(VTe_(2))exhibits a 2√3×2√3 charge-density-wave(CDW)order intertwined with a Mott-insulating state.However,the physical mechanisms driving the emergence of the CDW order and the Mott-insulating state are still not well understood.In this study,we systematically investigate the electronic band structure,phonon dispersion,and electron-phonon coupling(EPC)of monolayer VTe_(2)under applied biaxial strain.Our results reveal that the 2√3×2√3 CDW phase is metastable in free-standing monolayer VTe_(2)but becomes stabilized under compressive strain below ε=-2%.The formation of the CDW order originates predominantly from strong EPC,rather than from Fermi-surface nesting.The narrowing of the bandwidth due to the CDW order,combined with correlation effects associated with the V3d orbitals,collectively drive the system into a Mott-insulating state.Furthermore,we find that tensile strain suppresses the CDW order and induces a superconducting state above a critical strain threshold(ε=2%).These findings enhance our understanding of correlation physics in monolayer VTe_(2)and provide a pathway for strain-engineered manipulation of quantum phases in two-dimensional transition-metal dichalcogenides.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12374140,12494593,11790312,12004056,11774060,and 92065201)the National Key R&D Program of China(Grant No.2023YFA1406304)+2 种基金the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302803)the Fundamental Research Funds for the Central Universities of China(Grant Nos.2022CDJXY-002 and WK9990000103)the New Cornerstone Science Foundation.
文摘The complex symmetry breaking states in AV3Sb5 family have attracted extreme research attention,but controversy still exists,especially in the question of time reversal symmetry breaking of the charge density wave(CDW).Most recently,a chiral CDW has been suggested in kagome magnet FeGe,but the related study is very rare.Here,we use a scanning tunneling microscope to study the symmetry breaking behavior of both the short-and long-range CDWs in FeGe.Different from previous studies,our study reveals an isotropic long-range CDW without obvious symmetry breaking,while local rotational symmetry breaking appears in the short-range CDW,which may be related to the existence of strong structural disorders.Moreover,the charge distribution of the short-range CDW is inert to the applied external magnetic fields and the detailed spin arrangements of FeGe,inconsistent with the expectation of a chiral CDW associated with chiral flux.Our results rule out the existence of spontaneous chiral and rotational symmetry breaking in the CDW state of FeGe,putting strong constraints on the further understanding of CDW mechanism.
基金Supported by the National Basic Research Program of China under Grant Nos 2015CB921300 and 2012CB821404the National Key Research and Development Program of China under Grant Nos 2016YFA0300300 and 2016YFA0300404+1 种基金the National Natural Science Foundation of China under Grant Nos 11474323,11604372,11274368,91221102,11190022,11674326 and 91422303the Strategic Priority Research Program(B)of the Chinese Academy of Sciences under Grant No XDB07020000
文摘The structural features and three-dimensional nature of the charge density wave （CDW） state of the layered chalcogenide 1T-TaSe2-xTex （0≤x≤2.0） are characterized by Cs-corrected transmission electron microscopy measurements. Notable changes of both average structure and the CDW state arising from Te substitution for Se are clearly demonstrated in samples with x〉0.3. The commensurate CDW state characterized by the known star-of-David clustering in the 1T-TaSe2 crystal becomes visibly unstable with Te substitution and vanishes when x=0.3. The 1T-TaSe2-xTex （0.3≤x≤1.3） samples generally adopt a remarkable incommensurate CDW state with monoclinic distortion, which could be fundamentally in correlation with the strong qq-dependent electron-phonon coupling-induced period-lattice-distortion as identified in TaTe22. Systematic analysis demonstrates that the occurrence of superconductivity is related to the suppression of the commensurate CDW phase and the presence of discommensuration is an evident structural feature observed in the superconducting samples.
基金the National Key Research and Development Program of China(Grant Nos.2021YFA1400100,2020YFA0308800,and 2019YFA0308000)the National Natural Science Foundation of China(Grant Nos.92163206,62171035,62171035,61901038,61971035,61725107,and 61674171)+1 种基金the Beijing Nova Program from Beijing Municipal Science&Technology Commission(Grant No.Z211100002121072)the Beijing Natural Science Foundation(Grant Nos.Z190006 and 4192054)。
文摘Charge density wave(CDW)strongly affects the electronic properties of two-dimensional(2D)materials and can be tuned by phase engineering.Among 2D transitional metal dichalcogenides(TMDs),VTe_(2)was predicted to require small energy for its phase transition and shows unexpected CDW states in its T-phase.However,the CDW state of H-VTe_(2)has been barely reported.Here,we investigate the CDW states in monolayer(ML)H-VTe_(2),induced by phase-engineering from T-phase VTe_(2).The phase transition between T-and H-VTe_(2)is revealed with x-ray photoelectron spectroscopy(XPS)and scanning transmission electron microscopy(STEM)measurements.For H-VTe_(2),scanning tunneling microscope(STM)and low-energy electron diffraction(LEED)results show a robust 2√3×2√3CDW superlattice with a transition temperature above 450 K.Our findings provide a promising way for manipulating the CDWs in 2D materials and show great potential in its application of nanoelectronics.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 92165205, 11790311, 12004172, 11774152, 11604366, and 11634007)the National Key Research and Development Program of China (Grant Nos. 2018YFA0306800 and 2016YFA0300401)+1 种基金the Program of High-Level Entrepreneurial and Innovative Talents Introduction of Jiangsu Province, the Jiangsu Planned Projects for Postdoctoral Research Funds (Grant No. 2020Z172)the Natural Science Foundation of Jiangsu Province, China (Grant No. BK 20160397)。
文摘As a special order of electronic correlation induced by spatial modulation, the charge density wave(CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in various temperatures, we discover a hidden incommensurate stripe-like CDW order besides the(■) CDW phase at low-temperature of 4 K in the epitaxial monolayer 1T-VSe_(2) film. Combining the variable-temperature angle-resolved photoemission spectroscopic(ARPES) measurements, we discover a two-step transition of an anisotropic CDW gap structure that consists of two parts △_(1) and△_(2). The gap part ?1 that closes around ~ 150 K is accompanied with the vanish of the(√7×√3) CDW phase. While another momentum-dependent gap part △_(2) can survive up to ~ 340 K, and is suggested to the result of the incommensurate CDW phase. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure △_(1) +△_(2), which suggests different forming mechanisms between the(√7×√3) and the incommensurate CDW phases. Our findings provide significant information and deep understandings on the CDW phases in monolayer 1T-VSe_(2) film as a two-dimensional(2D) material.
基金Project supported by the National Young 1000-Talent Planthe National Natural Science Foundation of China(Grant Nos.61322407,11474058,and61674040)
文摘Recently, modifications of charge density wave（CDW） in two-dimensional（2D） show intriguing properties in quasi-2D materials such as layered transition metal dichalcogenides（TMDCs）. Optical, electrical transport measurements and scanning tunneling microscopy uncover the enormous difference on the many-body states when the thickness is reduced down to monolayer. However, the CDW in quasi-one-dimensional（1D） materials like transition metal trichalcogenides（TMTCs） is yet to be explored in low dimension whose mechanism is likely distinct from their quasi-2D counterparts.Here, we report a systematic study on the CDW properties of titanium trisulfide（TiS3）. Two phase transition temperatures were observed to decrease from 53 K（103 K） to 46 K（85 K） for the bulk and 〈 15-nm thick nanoribbon, respectively,which arises from the increased fluctuation effect across the chain in the nanoribbon structure, thereby destroying the CDW coherence. It also suggests a strong anisotropy of CDW states in quasi-1D TMTCs which is different from that in TMDCs.Remarkably, by using back gate of-30 V ～ 70 V in 15-nm device, we can tune the second transition temperature from110 K（at-30 V） to 93 K（at 70 V） owing to the altered electron concentration. Finally, the optical approach through the impinging of laser beams on the sample surface is exploited to manipulate the CDW transition, where the melting of the CDW states shows a strong dependence on the excitation energy. Our results demonstrate TiS3 as a promising quasi-1D CDW material and open up a new window for the study of collective phases in TMTCs.
基金the National Key Research and Development Program of China(Grant Nos.2018YFA0305700,2017YFA0403600,and2016YFA0401804)the National Natural Science Foundation of China(Grant Nos.U1632275,U19A2093,U1932152,U1632162,12004004,11874362,11804344,11704387,and 11674325)+4 种基金the Natural Science Foundation of Anhui Province,China(Grant Nos.1908085QA18,2008085QA40,and1808085MA06)the Users with Excellence Project of Hefei Science Center CAS(Grant Nos.2018HSC-UE012,2020HSC-CIP014,2020HSC-UE015,and2021HSC-UE008)the Major Program of Development Foundation of Hefei Center for Physical Science and Technology(Grant No.2018ZYFX002)supported by the High Magnetic Field Laboratory of Anhui Province(Grant No.AHHM-FX-2020-02)supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2020443)。
文摘Layered lanthanum silver antimonide LaAgSb_(2)exhibits both charge density wave(CDW)order and Dirac-cone-like band structure at ambient pressure.Here,we systematically investigate the pressure evolution of structural and electronic properties of LaAgSb_(2)single crystal.We show that the CDW order is destabilized under compression,as evidenced by the gradual suppression of magnetoresistance.At P_(C)~22 GPa,synchrotron x-ray diffraction and Raman scattering measurements reveal a structural modification at room-temperature.Meanwhile,the sign change of the Hall coefficient is observed at 5 K.Our results demonstrate the tunability of CDW order in the pressurized LaAgSb_(2)single crystal,which can be helpful for its potential applications in the next-generation devices.
基金supported by the National Natural Science Foundation of China(Grant Nos.22176181,11874306,and 12174320)the Foundation of Science and Technology on Surface Physics and Chemistry Laboratory(Grant No.WDZC202101)the Natural Science Foundation of Chongqing,China(Grant No.cstc2021jcyj-msxmX0209)。
文摘The effect of strain on charge density wave(CDW)order inα-U is investigated within the framework of relativistic density-functional theory.The energetical stability ofα-U with CDW distortion is enhanced by the tensile strain along a and b axes,which is similar to the case of negative pressure and normal.However,the tensile strain along c axis suppresses the energetical stability of CDW phase.This abnormal effect could be understood from the emergence of a new onedimensional atomic chain along c axis inα-U.Furthermore,this effect is supported by the calculations of Fermi surface and phonon mode,in which the topological objects and the dynamical instability show opposite behaviors between strains along a/b and c axes.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574338 and 12074038)NSAF(Grant No.U1530402)。
文摘Anisotropy is an important feature of layered materials,and a large anisotropy is usually related to the two-dimensional charac teristics.We investigated the anisotropy of the layered transition metal dicalcogenide 2H-NbSe_(2)in the superconducting and charge density wave(CDW)states using magnetotransport measurements.In the superconducting state,the normalized H_(c2)^(‖c)/H_(p)is independent of the thickness of 2H-NbSe_(2),while H_(c2)^(‖ab)/H_p increases significantly with decreasing thickness,where H_p is the Pauli limiting magnetic field and H_(c2)^(‖c)anu H_(c2)^(‖ab)are the upper critical fields in the c and ab directions,respectively.It is found that the superconducting anisotropy parameterγH_(c2)=H_(c2)^(‖ab)/H_(c2)^(‖c)increases with reduction in the thickness of 2H-NbSe_(2).In the CDW state,the angular(θ)dependence of magnetoresistance,R(H,θ)scales with H(cos^(2)θ+γ_(CDW)^(-2)sin^(2)θ)^(1/2),which decreases with increasing temperature and disappears at about 40 K.It is found that the CDW anisotropy parameterγ_(CDW)is much larger than the effective mass anisotropy but does not change a lot for ultrathin and bulk samples.Our results suggest the existence of three-dimensional superconductivity and quasi-two dimensional CDWs in bulk 2H-NbSe_(2).
基金Project supported by the National Key Research and Development Project of China(Grant No.2019YFA0308500)the National Natural Science Foundation of China(Grant No.61888102)the Chinese Academy of Sciences(Grant Nos.XDB30000000 and YSBR-003).
文摘Domain walls(DWs)in the charge-density-wave(CDW)Mott insulator 1T-TaS_(2)have unique localized states,which play an important role in exploring the electronic properties of the material.However,the electronic states in DWs in 1TTaS_(2)have not been clearly understood,mostly due to the complex structures,phases,and interlayer stacking orders in the DW areas.Here,we explored the electronic states of DWs in the large-area CDW phase and mosaic phase of 1T-TaS_(2)by scanning tunneling spectroscopy.Due to the different densities of DWs,the electronic states of DWs show distinct features in these phases.In the large area CDW phase,both the domain and the DWs(DW1,DW2,DW4)have zero conductance at the Fermi level;while in the mosaic phase,they can be metallic or insulating depending on their environments.In areas with a high density of DWs,some electronic states were observed both on the DWs and within the domains,indicating delocalized states over the whole region.Our work contributes to further understanding of the interplay between CDW and electron correlations in 1T-TaS_(2).
基金the National Key Research and Development Program of China(Grant No.2021YFA1400403)the National Natural Science Foundation of China(Grant Nos.92165205,11790311,and 11774149)+2 种基金Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302800)the support by the open project of Beijing National Laboratory for Condensed Matter Physics(Grant No.ZBJ2106110017)the Double First-Class Initiative Fund of Shanghai Tech University。
文摘Owing to the unique electronic structure,kagome materials AV_(3)Sb_(5)(A=K,Rb,Cs)provide a fertile platform of quantum phenomena such as the strongly correlated state and topological Dirac band.It is well known that RbV_(3)Sb_(5)exhibits a 2×2 unconventional charge density wave(CDW)state at low temperature,and the mechanism is controversial.Here,by using scanning tunneling microscopy/spectroscopy(STM/STS),we successfully manipulated the CDW state in the Sb plane of RbV_(3)Sb_(5),and realized a new3(1/2)×3(1/2)modulation together with the ubiquitous 2×2 period in the CDW state of RbV_(3)Sb_(5).This work provides a new understanding of the collective quantum ground states in the kagome materials.
文摘Thermodynamic properties of the charge density wave(CDW) transition in potassium blue bronze K 0.3 MoO 3 are investigated by the measurement of specific heat. A second order phase transition is observed at 177.5 K. The specific heat jump, and enthalpy and entropy changes associated with the transition are estimated. The results suggest that the lattice plays an important role in thermodynamics for this compound. Analysis of the data near CDW transition shows that width of critical region is about 6 K and the critical behavior belongs to the universality class of the three dimensional XY model.
基金supported by the National Natural Science Foundation of China (Grant No. 11874263)the National Key R&D Program of China (Grant No. 2017YFE0131300)Shanghai Technology Innovation Action Plan (2020-Integrated Circuit Technology Support Program 20DZ1100605,2021-Fundamental Research Area 21JC1404700)。
文摘We investigate the topological phase transition driven by non-local electronic correlations in a realistic quantum anomalous Hall model consisting of d_(xy)–d_(x^(2)-y^(2)) orbitals. Three topologically distinct phases defined in the noninteracting limit evolve to different charge density wave phases under correlations. Two conspicuous conclusions were obtained: The topological phase transition does not involve gap-closing and the dynamical fluctuations significantly suppress the charge order favored by the next nearest neighbor interaction. Our study sheds light on the stability of topological phase under electronic correlations, and we demonstrate a positive role played by dynamical fluctuations that is distinct to all previous studies on correlated topological states.
基金support from the National Key R&D Program of China(2021YFA1401800 and 2021YFA1400202)the National Natural Science Foundation of China(12141404)+7 种基金the Natural Science Foundation of Shanghai(22ZR1479700 and 23XD1422200)Shaofeng Duan acknowledged support from the China Postdoctoral Science Foundation(2022M722108)the China National Postdoctoral Program for Innovative Talents(BX20230216)the National Natural Science Foundation of China(12304178)Yanfeng Guo acknowledged the National Key R&D Program of China(2023YFA1406100)the Double First-Class Initiative Fund of ShanghaiTech Universitysupport from the National Key R&D Program of China(2022YFA1402400 and 2021YFA1400100)the National Natural Science Foundation of China(12074248).
文摘The kagome lattice,characterized by its network of cornersharing triangles,provides an excellent platform for studying various novel quantum phenomena.The recently discovered kagome metal AV3Sb5(A=K,Rb,Cs)[1]garners significant attention for its unique properties,including an unconventional charge density wave(CDW)and superconductivity(SC)[2],as well as the interplay between CDW and SC[3].
基金supported by the National Key Research and Development Projects of China(Grant Nos.2023YFA1406103,2024YFA1611302,2024YFA1409200,and 2022YFA1403402)the National Natural Science Foundation of China(Grant Nos.12374142,12304170,12025408,12404179,and U23A6003)+2 种基金Beijing National Laboratory for Condensed Matter Physics(Grant No.2024BNLCMPKF005)the Chinese Academy of Sciences President’s International Fellowship Initiative(Grant No.2024PG0003)supported by the Synergetic Extreme Condition User Facility(SECUF,https://cstr.cn/31123.02.SECUF)。
文摘The recent discovery of superconductivity in La_(3)Ni_(2)O_(7-δ)with a transition temperature Tc close to 80 K at high pressures has attracted significant attention,due particularly to a possible density wave(DW)transition occurring near the superconducting dome.Identifying the type of DW order is crucial for understanding the origin of superconductivity in this system.However,owing to the presence of La4Ni3O10 and other intergrowth phases in La_(3)Ni_(2)O_(7-δ)samples,extracting the intrinsic information from the La_(3)Ni_(2)O_(7) phase is challenging.In this study,we employed ^(139)La nuclear quadrupole resonance(NQR)measurements to eliminate the influence of other structural phases in the sample and obtain microscopic insights into the DW transition in La_(3)Ni_(2)O_(7-δ).Below the DW transition temperature T_(DW)∼153 K,we observe a distinct splitting in the±5/2↔±7/2 transition of the NQR resonance peak at the La(2)site,while only a line broadening is seen in the±3/2↔±5/2 transition peak.Through further analysis of the spectra,we show that the line splitting is due to a unidirectional charge modulation.A magnetic line broadening is also observed below T_(DW),accompanied by a large enhancement of the spin-lattice relaxation rate,indicating the formation of magnetically ordered moments in the DW state.Our results suggest a simultaneous formation of charge-and spin-density wave orders in La_(3)Ni_(2)O_(7-δ),thereby offering critical insights into the electronic correlations in Ni-based superconductors.
基金supported by the National Natural Science Foundation of China(Grant No.62488201)the National Key Research and Development Project of China(Grant No.2022YFA1204100)+1 种基金the Chinese Academy of Sciences Project for Young Scientists in Basic Research(Grant No.YSBR-003)the Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700).
文摘Recent advances in strain engineering have enabled unprecedented control over quantum states in strongly correlated magnetic systems.However,nanoscale strain modulation of charge density waves(CDWs)and magnetically excited states,which is crucial for atomically precise strain engineering and practical spintronic applications,remains unexplored.Here,we report the nanoscale strain effects on CDWs and low-energy electronic states in the van der Waals antiferromagnetic metal GdTe_(3),utilizing scanning tunneling microscopy/spectroscopy.Lowtemperature cleavage introduces local strains,resulting in the formation of nanoscale wrinkles on the GdTe_(3)surface.Atomic displacement analysis reveals two distinct types of wrinkles:Wrinkle-I,originating from unidirectional strain,and Wrinkle-II,dominated by shear strain.In Wrinkle-I,the tensile strain enhances the CDW gap,while the compressive strain induces a single low-energy magnetic state.Wrinkle-II switches the orientation of CDW,leading to the formation of an associated CDW domain wall.In addition,three low-energy magnetic states that exhibit magnetic field-dependent shifts and intensity variations emerge within the CDW gap around Wrinkle-II,indicative of a strain-tuned coupling between CDW order and localized 4f-electron magnetism.These findings establish nanoscale strain as a powerful tuning knob for manipulating intertwined electronic and magnetic excitations in correlated magnetic systems.
基金the National Natural Science Foundation of China (Grant No.12204298)the National Natural Science Foundation of China (Grant No.12074242)+4 种基金the National Natural Science Foundation of China (Grant No.12174334)the National Natural Science Foundation of China (Grant Nos.52272265,U1932217,11974246,and 12004252)the Science and Technology Commission of Shanghai Municipality (Grant No.21JC1402600)the Zhejiang Provincial Natural Science Foundation of China (Grant No.LQ23A040009)supported by the Deutsche Forschungsgemeinschaft (DFG,German Research Foundation) (Grant No.406658237)。
文摘Charge density wave(CDW) in kagome materials with the geometric frustration is able to carry unconventional characteristics.Recently, a CDW has been observed below the antiferromagnetic order in kagome FeGe, in which magnetism and CDW are intertwined to form an emergent quantum ground state. However, the CDW is only short-ranged and the structural modulation originating from it has yet to be determined experimentally. Here we realize a long-range CDW order by post-annealing process,and resolve the structure model through single crystal X-ray diffraction. Occupational disorder of Ge resulting from short-range CDW correlations above T_(CDW) is identified from structure refinements. The partial dimerization of Ge along the c axis is unveiled to be the dominant distortion for the CDW. Occupational disorder of Ge is also proved to exist in the CDW phase due to the random selection of partially dimerized Ge sites. Our work provides useful insights for understanding the unconventional nature of the CDW in FeGe.
