Topochemical fluorination introduces significant structural distortions and emerging properties in perovskite oxides via substituting oxygen with fluorine.However,the rapid fluorination process and the similarity betw...Topochemical fluorination introduces significant structural distortions and emerging properties in perovskite oxides via substituting oxygen with fluorine.However,the rapid fluorination process and the similarity between F and O render the O/F site occupation and local lattice evolution during fluorination unclear.Here we investigated the atomic-scale O/F exchange in La2CoO4and quantified the lattice distortion of three ordered structures:La_(2)CoO_(3.5)F,La_(2)CoO_(3)F_(2),and La_(2)CoO_(2.5)F_(3)by utilizing aberration-corrected electron microscopy.Atomic-resolved elemental mapping provides direct evidence for the O/F occupancy in interstitial and apical sites.We revealed that apical F ions induce significant octahedral tilting from 178°to 165°,linearly proportional to the occupancy rate;and cause the obvious change in the fine structure O K edge,meanwhile apical O is exchanged into interstitial sites.The strong octahedral tilt leads to the in-plane elongation of the[CoO_(4)F_(2)]octahedra.These findings elucidate the atomic-scale mechanisms of the entire fluorination process and highlight the significant role of F in tuning the octahedral tilt of functional oxides.展开更多
Recently,natural van der Waals heterostructures of(MnBi2 Te4)m(Bi2 Te3)n have been theoretically predicted and experimentally shown to host tunable magnetic properties and topologically nontrivial surface states.We sy...Recently,natural van der Waals heterostructures of(MnBi2 Te4)m(Bi2 Te3)n have been theoretically predicted and experimentally shown to host tunable magnetic properties and topologically nontrivial surface states.We systematically investigate both the structural and electronic responses of MnBi2 Te4 and MnBi4 Te7 to external pressure.In addition to the suppression of antiferromagnetic order,MnBi2 Te4 is found to undergo a metalsemiconductor-metal transition upon compression.The resistivity of MnBi4 Te7 changes dramatically under high pressure and a non-monotonic evolution of p(T)is observed.The nontrivial topology is proved to persist before the structural phase transition observed in the high-pressure regime.We find that the bulk and surface states respond differently to pressure,which is consistent with the non-monotonic change of the resistivity.Interestingly,a pressure-induced amorphous state is observed in MnBi2 Te4,while two high-pressure phase transitions are revealed in MnBi4 Te7.Our combined theoretical and experimental research establishes MnBi2 Te4 and MnBi4 Te7 as highly tunable magnetic topological insulators,in which phase transitions and new ground states emerge upon compression.展开更多
Exploration of exotic phenomena in magnetic topological systems is at the frontier of condensed matter physics,holding a significant promise for applications in topological spintronics.However,complex magnetic structu...Exploration of exotic phenomena in magnetic topological systems is at the frontier of condensed matter physics,holding a significant promise for applications in topological spintronics.However,complex magnetic structures carrying nontrivial topological properties hinder its progresses.Here,we investigate the pressure effect on the novel topological kagome magnets GdV_(6)Sn_(6) and TbV_(6)Sn_(6) to dig out the interplay between magnetic Gd/Tb layers and nonmagnetic V-based kagome sublattice.The pressure-tuned magnetic transition temperature Tm in both the compounds exhibit a turning point at the critical pressure P_(c),accompanied with a sign reversal in anomalous Hall effect(AHE).The separation of intrinsic and extrinsic contributions using the Tian-Ye-Jin scaling model suggests that the intrinsic mechanism originating from the electronic Berry curvature holds the priority in the competition with extrinsic mechanism in AHE.The above-mentioned findings can be attributed to the combined effect of pressure-tuned band topology and magnetic interaction in segregated layers.Our results provide a practical route to design and manipulate the intrinsic AHE in magnetic topological materials.展开更多
Magnetic CeTe_(2)achieving superconductivity under external pressure has received considerable attention.The intermingling of 4f and 5d electrons from Ce raised the speculation of an unconventional pairing mechanism a...Magnetic CeTe_(2)achieving superconductivity under external pressure has received considerable attention.The intermingling of 4f and 5d electrons from Ce raised the speculation of an unconventional pairing mechanism arising from magnetic fluctuations.Here,we address this speculation using a nonmagnetic 4f-electron-free LaTe_(2)as an example.No structural phase transition can be observed up to 35 GPa in the in situ synchrotron diffraction patterns.Subsequent high-pressure electrical measurements show that LaTe_(2)exhibits superconductivity at20 Gpa with its T_(c)(4.5 K)being two times higher than its Ce-counterpart.Detailed theoretical calculations reveal that charge transfer from the 4p orbitals of the planar square Te-Te network to the 5d orbitals of La is responsible for the emergence of superconductivity in LaTe_(2),as confirmed by Hall experiments.Furthermore,we study the modulation of q_(CDW)by Sb substitution and find a record high T_(c)^(onset)~6.5 K in LaTe_(1.6)Sb_(0.4).Our work provides an informative clue to comprehend the role of 5d-4p hybridization in the relationship between charge density wave(CDW)and superconductivity in these RETe_(2)(RE=rare-earth elements)compounds.展开更多
We report the structure and physical properties of two newly discovered compounds AV_(8)Sb_(12)and AV_(6)Sb_(6)(A=Cs,Rb),which have C_(2)(space group:Cmmm)and C_(3)(space group:R3 m)symmetry,respectively.The basic Vka...We report the structure and physical properties of two newly discovered compounds AV_(8)Sb_(12)and AV_(6)Sb_(6)(A=Cs,Rb),which have C_(2)(space group:Cmmm)and C_(3)(space group:R3 m)symmetry,respectively.The basic Vkagome unit appears in both compounds,but stacking differently.AV_(2)Sb_(2) layer is sandwiched between two V_(3)Sb_(5)layers in AV_(8)Sb_(12),altering the V-kagome lattice and lowering the symmetry of kagome layer from hexagonal to orthorhombic.In AV_(6)Sb_(6),the building block is a more complex slab made up of two half-V_(3)Sb_(5)layers that are intercalated by Cs cations along the c-axis.Transport property measurements demonstrate that both compounds are nonmagnetic metals,with carrier concentrations at around 10^(21)cm^(-3).No superconductivity has been observed in CsV_(8)Sb_(12)above 0.3 K under in situ pressure up to 46 GPa.Compared to CSV_(3)Sb_(5),theoretical calculations and angle-resolved photoemission spectroscopy reveal a quasi-two-dimensional electronic structure in CsV_(8)Sb_(12)with C_(2)symmetry and no van Hove singularities near the Fermi level.Our findings will stimulate more research into V-based kagome quantum materials.展开更多
We report the synthesis and superconducting properties of a layered cage compound Ba_(3)Rh_(4)Ge_(16).Similar to Ba_(3)Ir_(4)Ge_(16),the compound is composed of 2 D networks of cage units,formed by noncubic Rh-Ge buil...We report the synthesis and superconducting properties of a layered cage compound Ba_(3)Rh_(4)Ge_(16).Similar to Ba_(3)Ir_(4)Ge_(16),the compound is composed of 2 D networks of cage units,formed by noncubic Rh-Ge building blocks,in marked contrast to the reported rattling compounds.The electrical resistivity,magnetization,specific heat capacity,andμSR measurements unveiled moderately coupled s-wave superconductivity with a critical temperature T_(c)=7.0 K,the upper critical field μ_(0)H_(c2)(0)~2.5 T,the electron-phonon coupling strength λ_(e-ph)~0.80,and the Ginzburg-Landau parameterκ~7.89.The mass reduction with the substitution of Ir by Rh is believed to be responsible for the enhancement of T_(c) and coupling between the cage and vip atoms.Our results highlight the importance of atomic weight of framework in cage compounds in controlling the λ_(e-ph) strength and T_(c).展开更多
Clathrate-like or caged compounds have attracted great interest owing to their structural flexibility,as well as their fertile physical properties.Here,we report the pressure-induced reemergence of superconductivity i...Clathrate-like or caged compounds have attracted great interest owing to their structural flexibility,as well as their fertile physical properties.Here,we report the pressure-induced reemergence of superconductivity in BaIr2Ge7 and Ba3Ir4Ge16,two new caged superconductors with two-dimensional building blocks of cage structures.After suppression of the ambient-pressure superconducting(SC-I)states,new superconducting(SC-II)states emerge unexpectedly,with Tc increased to a maximum of 4.4 and 4.0 K for BaIr2Ge7 and Ba3Ir4Ge16,respectively.Combined with high-pressure synchrotron x-ray diffraction and Raman measurements,we propose that the reemergence of superconductivity in these caged superconductors can be ascribed to a pressure-induced phonon softening linked to cage shrinkage.展开更多
The lunar soils evolution over time is mainly caused by space weathering that includes the impacts of varying-sized meteoroids and charged particles implantation of solar/cosmic winds as well.It has long been establis...The lunar soils evolution over time is mainly caused by space weathering that includes the impacts of varying-sized meteoroids and charged particles implantation of solar/cosmic winds as well.It has long been established that space weathering leads to the formation of outmost amorphous layers(50–200 nm in thickness)embedded nanophase iron(npFe^(0))around the mineral fragments,albeit the origin of the npFe^(0) remains controversial.The Chang’e-5(CE-5)mission returned samples feature the youngest mare basalt and the highest latitude sampling site,providing an opportunity to seek the critical clues for understanding the evolution of soils under space weathering.Here,we report the surface microstructures of the major minerals including olivine,pyroxene,anorthite,and glassy beads in the lunar soil of CE-5.Unlike the previous observations,only olivine in all crystals is surrounded by a thinner outmost amorphous SiO_(2) layer(∼10 nm thick)and embedded wüstite nanoparticles FeO(np-FeO,3–12 nm in size)instead of npFe^(0).No foreign volatile elements deposition layer and solar flare tracks can be found on the surface or inside the olivine and other minerals.This unique rim structure has not been reported for any other lunar,terrestrial,Martian,or meteorite samples so far.The observation of wüstite FeO and the microstructures support the existence of an intermediate stage in space weathering for lunar minerals by thermal decomposition.展开更多
Vacancies are prevalent and versatile in solid-state physics and materials science.The role of vacancies in strongly correlated materials,however,remains uncultivated until now.Here,we report the discovery of an unpre...Vacancies are prevalent and versatile in solid-state physics and materials science.The role of vacancies in strongly correlated materials,however,remains uncultivated until now.Here,we report the discovery of an unprecedented vacancy state forming an extended buckled-honeycomb-vacancy(BHV)ordering in Ir16Sb18.Superconductivity emerges by suppressing the BHV ordering through squeezing of extra Ir atoms into the vacancies or isovalent Rh substitution.The phase diagram on vacancy ordering reveals the superconductivity competes with the BHV ordering.Further theoretical calculations suggest that this ordering originates from a synergistic effect of the vacancy formation energy and Fermi surface nesting with a wave vector of(1/3,1/3,0).The buckled structure breaks the crystal inversion symmetry and can mostly suppress the density of states near the Fermi level.The peculiarities of BHV ordering highlight the importance of"correlated vacancies"and may serve as a paradigm for exploring other non-trivial excitations and quantum criticality.展开更多
Pyroelectrics are a class of polar compounds that output electrical signals upon changes in temperature.With the rapid development of flexible electronics,organic pyroelectrics are highly desired.However,most organics...Pyroelectrics are a class of polar compounds that output electrical signals upon changes in temperature.With the rapid development of flexible electronics,organic pyroelectrics are highly desired.However,most organics suffer from low pyroelectric coefficients or low working temperatures.To date,the realization of superior pyroelectric performance in all-organics has remained a challenge.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52322212,52025025,5225040212474001)the National Key R&D Program of China(Grant Nos.2022YFA1403203 and 2023YFA1406300)。
文摘Topochemical fluorination introduces significant structural distortions and emerging properties in perovskite oxides via substituting oxygen with fluorine.However,the rapid fluorination process and the similarity between F and O render the O/F site occupation and local lattice evolution during fluorination unclear.Here we investigated the atomic-scale O/F exchange in La2CoO4and quantified the lattice distortion of three ordered structures:La_(2)CoO_(3.5)F,La_(2)CoO_(3)F_(2),and La_(2)CoO_(2.5)F_(3)by utilizing aberration-corrected electron microscopy.Atomic-resolved elemental mapping provides direct evidence for the O/F occupancy in interstitial and apical sites.We revealed that apical F ions induce significant octahedral tilting from 178°to 165°,linearly proportional to the occupancy rate;and cause the obvious change in the fine structure O K edge,meanwhile apical O is exchanged into interstitial sites.The strong octahedral tilt leads to the in-plane elongation of the[CoO_(4)F_(2)]octahedra.These findings elucidate the atomic-scale mechanisms of the entire fluorination process and highlight the significant role of F in tuning the octahedral tilt of functional oxides.
基金Supported by the National Key Research and Development Program of China under Grant Nos.2018YFA0704300 and2017YFE0131300the National Natural Science Foundation of China under Grant Nos.U1932217,11974246,11874263 and10225417+1 种基金the Natural Science Foundation of Shanghai under Grant No.19ZR1477300the support from Analytical Instrumentation Center(SPST-AIC10112914),SPST,ShanghaiTech Universitysupported by Collaborative Research Project of Materials and Structures Laboratory,Tokyo Institute of Technology,Japan,Part of this research is supported by COMPRES(NSF Cooperative Agreement EAR-1661511)。
文摘Recently,natural van der Waals heterostructures of(MnBi2 Te4)m(Bi2 Te3)n have been theoretically predicted and experimentally shown to host tunable magnetic properties and topologically nontrivial surface states.We systematically investigate both the structural and electronic responses of MnBi2 Te4 and MnBi4 Te7 to external pressure.In addition to the suppression of antiferromagnetic order,MnBi2 Te4 is found to undergo a metalsemiconductor-metal transition upon compression.The resistivity of MnBi4 Te7 changes dramatically under high pressure and a non-monotonic evolution of p(T)is observed.The nontrivial topology is proved to persist before the structural phase transition observed in the high-pressure regime.We find that the bulk and surface states respond differently to pressure,which is consistent with the non-monotonic change of the resistivity.Interestingly,a pressure-induced amorphous state is observed in MnBi2 Te4,while two high-pressure phase transitions are revealed in MnBi4 Te7.Our combined theoretical and experimental research establishes MnBi2 Te4 and MnBi4 Te7 as highly tunable magnetic topological insulators,in which phase transitions and new ground states emerge upon compression.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1402203)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)+5 种基金supported by the National Key R&D Program of China(Grants No.2023YFA1406100)the Double First-Class Initiative Fund of ShanghaiTech Universitysupported by the National Natural Science Foundation of China(Grant No.52272265)supported by the National Science Basic Research Plan in the Shaanxi Province of China(Grant No.2024JC-YBQN-0390)supported by the open project from State Key Laboratory of Surface Physics and Department of Physics,Fudan University(Grant No.KF2022-13)supported by the National Natural Science Foundation of China(Grant No.52302010)。
文摘Exploration of exotic phenomena in magnetic topological systems is at the frontier of condensed matter physics,holding a significant promise for applications in topological spintronics.However,complex magnetic structures carrying nontrivial topological properties hinder its progresses.Here,we investigate the pressure effect on the novel topological kagome magnets GdV_(6)Sn_(6) and TbV_(6)Sn_(6) to dig out the interplay between magnetic Gd/Tb layers and nonmagnetic V-based kagome sublattice.The pressure-tuned magnetic transition temperature Tm in both the compounds exhibit a turning point at the critical pressure P_(c),accompanied with a sign reversal in anomalous Hall effect(AHE).The separation of intrinsic and extrinsic contributions using the Tian-Ye-Jin scaling model suggests that the intrinsic mechanism originating from the electronic Berry curvature holds the priority in the competition with extrinsic mechanism in AHE.The above-mentioned findings can be attributed to the combined effect of pressure-tuned band topology and magnetic interaction in segregated layers.Our results provide a practical route to design and manipulate the intrinsic AHE in magnetic topological materials.
基金financially supported by the National Key Research and Development Program of China(Grant Nos.2018YFE0202600,2021YFA1401800,2017YFA0304700)the National Natural Science Foundation of China(Grant Nos.51922105,11804184,11974208,11774424,12174443,U1932217,and11974246)+1 种基金Beijing Natural Science Foundation(Grant No.Z200005)supported by the Synergetic Extreme Condition User Facility(SECUF)。
文摘Magnetic CeTe_(2)achieving superconductivity under external pressure has received considerable attention.The intermingling of 4f and 5d electrons from Ce raised the speculation of an unconventional pairing mechanism arising from magnetic fluctuations.Here,we address this speculation using a nonmagnetic 4f-electron-free LaTe_(2)as an example.No structural phase transition can be observed up to 35 GPa in the in situ synchrotron diffraction patterns.Subsequent high-pressure electrical measurements show that LaTe_(2)exhibits superconductivity at20 Gpa with its T_(c)(4.5 K)being two times higher than its Ce-counterpart.Detailed theoretical calculations reveal that charge transfer from the 4p orbitals of the planar square Te-Te network to the 5d orbitals of La is responsible for the emergence of superconductivity in LaTe_(2),as confirmed by Hall experiments.Furthermore,we study the modulation of q_(CDW)by Sb substitution and find a record high T_(c)^(onset)~6.5 K in LaTe_(1.6)Sb_(0.4).Our work provides an informative clue to comprehend the role of 5d-4p hybridization in the relationship between charge density wave(CDW)and superconductivity in these RETe_(2)(RE=rare-earth elements)compounds.
基金Supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0304700 and 2018YFE0202601)the National Natural Science Foundation of China(Grant Nos.51922105,51772322,52025025,and 52072400)the Beijing Natural Science Foundation(Grant No.Z200005)。
文摘We report the structure and physical properties of two newly discovered compounds AV_(8)Sb_(12)and AV_(6)Sb_(6)(A=Cs,Rb),which have C_(2)(space group:Cmmm)and C_(3)(space group:R3 m)symmetry,respectively.The basic Vkagome unit appears in both compounds,but stacking differently.AV_(2)Sb_(2) layer is sandwiched between two V_(3)Sb_(5)layers in AV_(8)Sb_(12),altering the V-kagome lattice and lowering the symmetry of kagome layer from hexagonal to orthorhombic.In AV_(6)Sb_(6),the building block is a more complex slab made up of two half-V_(3)Sb_(5)layers that are intercalated by Cs cations along the c-axis.Transport property measurements demonstrate that both compounds are nonmagnetic metals,with carrier concentrations at around 10^(21)cm^(-3).No superconductivity has been observed in CsV_(8)Sb_(12)above 0.3 K under in situ pressure up to 46 GPa.Compared to CSV_(3)Sb_(5),theoretical calculations and angle-resolved photoemission spectroscopy reveal a quasi-two-dimensional electronic structure in CsV_(8)Sb_(12)with C_(2)symmetry and no van Hove singularities near the Fermi level.Our findings will stimulate more research into V-based kagome quantum materials.
基金Supported the National Key R&D Program of China(Grant No.2018YFA0704300)the National Natural Science Foundation of China(Grant Nos.U1932217,11974246,and 12004252)+5 种基金the Natural Science Foundation of Shanghai(Grant No.19ZR1477300)the Science and Technology Commission of Shanghai Municipality(Grant No.19JC1413900)the Analytical Instrumentation Center,SPST,Shanghai Tech University(Grant No.SPST-AIC10112914)the SERB,India for Core Research grant supportUK-India Newton Funding for funding supportthe Royal Society of London for Newton Advanced Fellowship funding and International Exchange funding between UK and JapanISIS Facility for beam time(Grant No.RB1968041)。
文摘We report the synthesis and superconducting properties of a layered cage compound Ba_(3)Rh_(4)Ge_(16).Similar to Ba_(3)Ir_(4)Ge_(16),the compound is composed of 2 D networks of cage units,formed by noncubic Rh-Ge building blocks,in marked contrast to the reported rattling compounds.The electrical resistivity,magnetization,specific heat capacity,andμSR measurements unveiled moderately coupled s-wave superconductivity with a critical temperature T_(c)=7.0 K,the upper critical field μ_(0)H_(c2)(0)~2.5 T,the electron-phonon coupling strength λ_(e-ph)~0.80,and the Ginzburg-Landau parameterκ~7.89.The mass reduction with the substitution of Ir by Rh is believed to be responsible for the enhancement of T_(c) and coupling between the cage and vip atoms.Our results highlight the importance of atomic weight of framework in cage compounds in controlling the λ_(e-ph) strength and T_(c).
基金the National Natural Science Foundation of China(Grant Nos.U1932217,11974246,and 12004252)the National Key R&D Program of China(Grant No.2018YFA0704300)+3 种基金the Natural Science Foundation of Shanghai(Grant No.19ZR1477300)the Science and Technology Commission of Shanghai Municipality(Grant No.19JC1413900)the Shanghai Science and Technology Plan(Grant No.21DZ2260400)the Analytical Instrumentation Center(Grant No.SPST-AIC10112914),SPST,ShanghaiTech University.
文摘Clathrate-like or caged compounds have attracted great interest owing to their structural flexibility,as well as their fertile physical properties.Here,we report the pressure-induced reemergence of superconductivity in BaIr2Ge7 and Ba3Ir4Ge16,two new caged superconductors with two-dimensional building blocks of cage structures.After suppression of the ambient-pressure superconducting(SC-I)states,new superconducting(SC-II)states emerge unexpectedly,with Tc increased to a maximum of 4.4 and 4.0 K for BaIr2Ge7 and Ba3Ir4Ge16,respectively.Combined with high-pressure synchrotron x-ray diffraction and Raman measurements,we propose that the reemergence of superconductivity in these caged superconductors can be ascribed to a pressure-induced phonon softening linked to cage shrinkage.
基金supported by the Key Research Program of Chinese Academy of Sciences(ZDBS-SSW-JSC007-2)the Project from China National Space Administration(CE5C0400YJFM00507)。
文摘The lunar soils evolution over time is mainly caused by space weathering that includes the impacts of varying-sized meteoroids and charged particles implantation of solar/cosmic winds as well.It has long been established that space weathering leads to the formation of outmost amorphous layers(50–200 nm in thickness)embedded nanophase iron(npFe^(0))around the mineral fragments,albeit the origin of the npFe^(0) remains controversial.The Chang’e-5(CE-5)mission returned samples feature the youngest mare basalt and the highest latitude sampling site,providing an opportunity to seek the critical clues for understanding the evolution of soils under space weathering.Here,we report the surface microstructures of the major minerals including olivine,pyroxene,anorthite,and glassy beads in the lunar soil of CE-5.Unlike the previous observations,only olivine in all crystals is surrounded by a thinner outmost amorphous SiO_(2) layer(∼10 nm thick)and embedded wüstite nanoparticles FeO(np-FeO,3–12 nm in size)instead of npFe^(0).No foreign volatile elements deposition layer and solar flare tracks can be found on the surface or inside the olivine and other minerals.This unique rim structure has not been reported for any other lunar,terrestrial,Martian,or meteorite samples so far.The observation of wüstite FeO and the microstructures support the existence of an intermediate stage in space weathering for lunar minerals by thermal decomposition.
基金supported by the National Natural Science Foundation of China(12004252,52272265,U1932217,11974246,52072400,52025025,and 92065109)the National Key R&D Program of China(2018YFA0704300,2021YFA1401800,2018YFE0202601,2020YFA0308800,and 2022YFA1403400)+2 种基金Shanghai Science and Technology Plan(21DZ2260400)Beijing Natural Science Foundation(Z190010,Z210006,and Z190006)the support from the Analytical Instrumentation Center(#SPST-AIC10112914),School of Physical Science and Technology(SPST),ShanghaiTech University。
基金support by the National Key Research and Development Program of China(2018YFA0704300)the National Natural Science Foundation of China(U1932217 and 11974246)+4 种基金the Natural Science Foundation of Shanghai(19ZR1477300)supported by MEXT Element Strategy Initiative to form Core Research Centerpartially supported by ChEM,SPST of ShanghaiTech University(02161943)Analytical Instrumentation Center(SPST-AIC10112914),SPST of ShanghaiTech Universitysupported by the National Natural Science Foundation of China(11888101)。
文摘Vacancies are prevalent and versatile in solid-state physics and materials science.The role of vacancies in strongly correlated materials,however,remains uncultivated until now.Here,we report the discovery of an unprecedented vacancy state forming an extended buckled-honeycomb-vacancy(BHV)ordering in Ir16Sb18.Superconductivity emerges by suppressing the BHV ordering through squeezing of extra Ir atoms into the vacancies or isovalent Rh substitution.The phase diagram on vacancy ordering reveals the superconductivity competes with the BHV ordering.Further theoretical calculations suggest that this ordering originates from a synergistic effect of the vacancy formation energy and Fermi surface nesting with a wave vector of(1/3,1/3,0).The buckled structure breaks the crystal inversion symmetry and can mostly suppress the density of states near the Fermi level.The peculiarities of BHV ordering highlight the importance of"correlated vacancies"and may serve as a paradigm for exploring other non-trivial excitations and quantum criticality.
基金This work is financially supported by the National Key Research and Development Program of China(2018YFE0202600,2016YFA0300301),the National Natural Science Foundation of China under granting numbers:No.51532010,91422303,51772323and the Key Research Program of Frontier Sciences,CAS,Grant No.QYZDJ-SSW-SLH013.
文摘Pyroelectrics are a class of polar compounds that output electrical signals upon changes in temperature.With the rapid development of flexible electronics,organic pyroelectrics are highly desired.However,most organics suffer from low pyroelectric coefficients or low working temperatures.To date,the realization of superior pyroelectric performance in all-organics has remained a challenge.
