The kagome superconductor CsV_(3)Sb_(5) has attracted widespread attention due to its rich correlated electron states including superconductivity, charge density wave(CDW), nematicity, and pair density wave. Notably, ...The kagome superconductor CsV_(3)Sb_(5) has attracted widespread attention due to its rich correlated electron states including superconductivity, charge density wave(CDW), nematicity, and pair density wave. Notably, the modulation of the intertwined electronic orders by the chemical doping is significant to illuminate the cooperation/competition between multiple phases in kagome superconductors. In this study, we have synthesized a series of tantalum-substituted Cs(V_(1-x)Ta_(x))_(3)Sb_(5) by a modified self-flux method. Electrical transport measurements reveal that CDW is suppressed gradually and becomes undetectable as the doping content of x is over 0.07. Concurrently, the superconductivity is enhanced monotonically from T_(c) ~ 2.8 K at x = 0 to 5.2 K at x = 0.12. Intriguingly, in the absence of CDW, Cs(V_(1-x)Ta_(x))_(3)Sb_(5)(x = 0.12) crystals exhibit a pronounced two-fold symmetry of the in-plane angular-dependent magnetoresistance(AMR) in the superconducting state, indicating the anisotropic superconducting properties in the Cs(V_(1-x)Ta_(x))_(3)Sb_(5). Our findings demonstrate that Cs(V_(1-x)Ta_(x))_(3)Sb_(5) with the non-trivial band topology is an excellent platform to explore the superconductivity mechanism and intertwined electronic orders in quantum materials.展开更多
EuB_(6),a magnetic topological semimetal,has attracted considerable attention in recent years due to its rich intriguing physical properties,including a colossal negative magnetoresistance(CNMR)ratio exceeding-80%,a t...EuB_(6),a magnetic topological semimetal,has attracted considerable attention in recent years due to its rich intriguing physical properties,including a colossal negative magnetoresistance(CNMR)ratio exceeding-80%,a topological phase transition and a predicted quantum anomalous Hall effect(QAHE)approaching the two-dimensional(2D)limit.Yet,studies of the influence of the dimensionality approaching 2D on the electronic transport properties of EuB_(6) are still scarce.In this work,EuB_(6) thin sheets with thicknesses ranging from 35μm to 180μm were successfully fabricated through careful mechanical polishing of high-quality EuB_(6) single crystals.The reduced thickness,temperature and magnetic field have a strong influence on the electronic transport properties,including the CNMR and carrier concentration of EuB_(6) thin sheets.As the thickness of EuB_(6) thin sheets decreases from 180μm to 35μm,the magnetization transition temperature and the corresponding suppressing temperature of the Kondo effect decrease from 15.2 K to 10.9 K,while the CNMR ratio increases from-87.2%to-90.8%.Furthermore,the weak antilocalization effect transits to a weak localization effect and the carrier concentration increases by 9.4%at 30 K in a 35μm EuB_(6) thin sheet compared to the value reported for a 180μm thin sheet.Our findings demonstrate an obvious tunable effect of the reduced dimensionality on the transport properties of EuB_(6) along with the temperature and magnetic field,which could provide a route to exploring the QAHE near the 2D limit in EuB_(6) and other topological semimetals.展开更多
Vanadium-based transition metal chalcogenides VmXn(X=S,Se,Te)with their distinctive quantum effects,tunable magnetism,spin-orbit coupling,and high carrier mobility are a valuable platform to explore the interplay betw...Vanadium-based transition metal chalcogenides VmXn(X=S,Se,Te)with their distinctive quantum effects,tunable magnetism,spin-orbit coupling,and high carrier mobility are a valuable platform to explore the interplay between magnetism and electronic correlations,especially with tunable structural phases and magnetic properties through stoichiometric variations,making them ideal candidates for advanced device applications.Here,we report the synthesis of high-quality V_(5+x)S_(8)single crystals with different concentrations of self-intercalated vanadium.V_(5+x)S_(8)crystals show an antiferromagnetic behavior and a spin-flop-like transition below TN of 30.6 K.The high-quality V_(5+x)S_(8)single crystals exhibit a large negative magnetoresistance of 12.3%at 2 K.Interestingly,V_(5+x)S_(8)crystals show an obvious low-temperature resistance upturn that gradually levels off with the increasing magnetic field,attributed to the Kondo effect arising from the interaction between conduction electrons and embedded vanadium magnetic impurities.With increasing V doping,the antiferromagnetic interactions intensify,weakening the coupling between the local moments and conduction electrons,which in turn lowers the Kondo temperature(TK).Furthermore,the anomalous Hall effect is observed in V5.73S8,with an anomalous Hall conductivity(AHC)of 50.46 W^(-1)·cm^(-1)and anomalous Hall angle of 0.73%at 2 K.Our findings offer valuable insights into the mechanisms of the Kondo effect and anomalous Hall effect in self-intercalated transition metal chalcogenides with complex magnetism and electronic correlation effects.展开更多
Ising superconductivity, induced by the strong spin–orbit coupling(SOC) and inversion symmetry breaking, can lead to the in-plane upper critical field exceeding the Pauli limit and hold significant potential for adva...Ising superconductivity, induced by the strong spin–orbit coupling(SOC) and inversion symmetry breaking, can lead to the in-plane upper critical field exceeding the Pauli limit and hold significant potential for advancing the study of topological superconductivity. However, the enhancement of Ising superconductivity is still a challenging problem, important for engineering Majorana fermions and exploring topological quantum computing. In this study, we investigated the superconducting properties of a series of van der Waals NbSe_(2-x)Te_(x) nanosheets. The Ising superconductivity in NbSe_(2-x)Te_(x) nanosheets can be significantly enhanced by the substitution of Te, an element with strong SOC. The fitted in-plane upper critical field of Nb Se_(1.5)Te_(0.5) nanosheets at absolute zero temperature reaches up to 3.2 times the Pauli limit. Angular dependence of magnetoresistance measurements reveals a distinct two-fold rotational symmetry in the superconducting transition region, highlighting the role of strong SOC. In addition, the fitting results of the Berezinskii–Kosterlitz–Thouless(BKT) transition and the two-dimensional(2D) Tinkham formula provide strong evidence for 2D superconductivity. These findings offer new perspectives for the design and modulation of the Ising superconducting state and pave the way for their potential applications in topological superconductivity and quantum technologies.展开更多
Two-dimensional van der Waals(vdW)magnetic materials,characterized by their tunable magnetism,spin transport properties,and remarkable quantum effects,provide significant promise for the development of efficient,low-p...Two-dimensional van der Waals(vdW)magnetic materials,characterized by their tunable magnetism,spin transport properties,and remarkable quantum effects,provide significant promise for the development of efficient,low-power spintronic devices.Intriguingly,the rare earth tritelluride(RTe3)materials have attracted great attention due to their unique magnetic structure,exotic electronic properties,multiple charge density wave(CDW),and superconductivity under pressure.Here,we report the successful synthesis of high-quality DyTe_(3)single crystals using a self-flux method.DyTe_(3)shows an antiferromagnetic transition at 4.5 K and demonstrates the magnetic field-induced ferromagnetism.The high-quality DyTe_(3)single crystal demonstrates outstanding transport properties,featuring a high carrier mobility of approximately1.4×10^(4)cm^(2)·V^(-1)·s^(-1)and large linear magnetoresistance of 1300%.Furthermore,distinct Shubnikov-de Haas(SdH)oscillations are observed in DyTe_(3),revealing a small Fermi pocket and an effective mass of 0.24 me.Remarkably,the unconventional in-plane negative magnetoresistances appear along the a-axis below 2 T and c-axis until 9 T from 2 K to17 K,which are attributed to the complex helimagnetic structures caused by CDW coupling and weak single-ion anisotropy.Our findings offer a significant platform for understanding the complex magnetoresistance behavior and quantum transport effects in RTe3-type materials,holding great promise for advancing applications in electronic and spintronic devices.展开更多
Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of...Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of Bi_(4)Br_(4) are limited, and its broadband absorption capabilities have not been validated. This study presents the first preparation of Bi_(4)Br_(4) samples using the chemical vapor transport method, resulting in a saturable absorber(SA) with a high modulation depth(46.23%) and low non-saturable loss(6.5%). The optical nonlinearity ranks among the best in similar studies. Additionally, this work applies Bi_(4)Br_(4)-SA for the first time in 1-μm fiber laser, developing a ring-cavity mode-locked fiber laser with a central wavelength of 1029.79 nm, a pulse duration of 442 fs, and a maximum output power of 90.83 m W. And a linear-cavity mode-locked fiber laser with a central wavelength of 1031.24 nm, a pulse duration of 511 fs, and a maximum output power of 92.81 m W is constructed. It is worth noting that the optical-to-optical conversion efficiency has reached about 11.54% and 33.58%.This study verifies Bi_(4)Br_(4)-SA's modulation effectiveness for 1-μm pulse lasers and provides a powerful reference for the design of high-efficiency fiber lasers.展开更多
Two-dimensional(2D)magnet/superconductor heterostructures can promote the design of artificial materials for exploring 2D physics and device applications by exotic proximity effects.However,plagued by the low Curie te...Two-dimensional(2D)magnet/superconductor heterostructures can promote the design of artificial materials for exploring 2D physics and device applications by exotic proximity effects.However,plagued by the low Curie temperature and instability in air,it is hard to realize practical applications for the reported layered magnetic materials at present.In this paper,we developed a space-confined chemical vapor deposition method to synthesize ultrathin air-stable ε-Fe_(2)O_(3) nanosheets with Curie temperature above 350 K.The ε-Fe_(2)O_(3)/NbSe_(2) heterojunction was constructed to study the magnetic proximity effect on the superconductivity of the NbSe_(2) multilayer.The electrical transport results show that the subtle proximity effect can modulate the interfacial spin–orbit interaction while undegrading the superconducting critical parameters.Our work paves the way to construct 2D heterojunctions with ultrathin nonlayered materials and layered van der Waals(vdW)materials for exploring new physical phenomena.展开更多
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1204100)the National Natural Science Foundation of China(Grant No.62488201)+1 种基金the Chinese Academy of Sciences(Grant Nos.XDB33030000,ZDBS-SSW-WHC001,YSBR-003,and YSBR-053)Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘The kagome superconductor CsV_(3)Sb_(5) has attracted widespread attention due to its rich correlated electron states including superconductivity, charge density wave(CDW), nematicity, and pair density wave. Notably, the modulation of the intertwined electronic orders by the chemical doping is significant to illuminate the cooperation/competition between multiple phases in kagome superconductors. In this study, we have synthesized a series of tantalum-substituted Cs(V_(1-x)Ta_(x))_(3)Sb_(5) by a modified self-flux method. Electrical transport measurements reveal that CDW is suppressed gradually and becomes undetectable as the doping content of x is over 0.07. Concurrently, the superconductivity is enhanced monotonically from T_(c) ~ 2.8 K at x = 0 to 5.2 K at x = 0.12. Intriguingly, in the absence of CDW, Cs(V_(1-x)Ta_(x))_(3)Sb_(5)(x = 0.12) crystals exhibit a pronounced two-fold symmetry of the in-plane angular-dependent magnetoresistance(AMR) in the superconducting state, indicating the anisotropic superconducting properties in the Cs(V_(1-x)Ta_(x))_(3)Sb_(5). Our findings demonstrate that Cs(V_(1-x)Ta_(x))_(3)Sb_(5) with the non-trivial band topology is an excellent platform to explore the superconductivity mechanism and intertwined electronic orders in quantum materials.
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1204100)the National Natural Science Foundation of China(Grant No.62488201)+1 种基金the Chinese Academy of Sciences(Grant Nos.XDB33030000 and YSBR-053)Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘EuB_(6),a magnetic topological semimetal,has attracted considerable attention in recent years due to its rich intriguing physical properties,including a colossal negative magnetoresistance(CNMR)ratio exceeding-80%,a topological phase transition and a predicted quantum anomalous Hall effect(QAHE)approaching the two-dimensional(2D)limit.Yet,studies of the influence of the dimensionality approaching 2D on the electronic transport properties of EuB_(6) are still scarce.In this work,EuB_(6) thin sheets with thicknesses ranging from 35μm to 180μm were successfully fabricated through careful mechanical polishing of high-quality EuB_(6) single crystals.The reduced thickness,temperature and magnetic field have a strong influence on the electronic transport properties,including the CNMR and carrier concentration of EuB_(6) thin sheets.As the thickness of EuB_(6) thin sheets decreases from 180μm to 35μm,the magnetization transition temperature and the corresponding suppressing temperature of the Kondo effect decrease from 15.2 K to 10.9 K,while the CNMR ratio increases from-87.2%to-90.8%.Furthermore,the weak antilocalization effect transits to a weak localization effect and the carrier concentration increases by 9.4%at 30 K in a 35μm EuB_(6) thin sheet compared to the value reported for a 180μm thin sheet.Our findings demonstrate an obvious tunable effect of the reduced dimensionality on the transport properties of EuB_(6) along with the temperature and magnetic field,which could provide a route to exploring the QAHE near the 2D limit in EuB_(6) and other topological semimetals.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1204100)the National Natural Science Foundation of China(Grant Nos.62488201 and 1240041502)+2 种基金the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-003)the Chinese Academy of Sciences(Grant No.XDB33030100)the Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700).
文摘Vanadium-based transition metal chalcogenides VmXn(X=S,Se,Te)with their distinctive quantum effects,tunable magnetism,spin-orbit coupling,and high carrier mobility are a valuable platform to explore the interplay between magnetism and electronic correlations,especially with tunable structural phases and magnetic properties through stoichiometric variations,making them ideal candidates for advanced device applications.Here,we report the synthesis of high-quality V_(5+x)S_(8)single crystals with different concentrations of self-intercalated vanadium.V_(5+x)S_(8)crystals show an antiferromagnetic behavior and a spin-flop-like transition below TN of 30.6 K.The high-quality V_(5+x)S_(8)single crystals exhibit a large negative magnetoresistance of 12.3%at 2 K.Interestingly,V_(5+x)S_(8)crystals show an obvious low-temperature resistance upturn that gradually levels off with the increasing magnetic field,attributed to the Kondo effect arising from the interaction between conduction electrons and embedded vanadium magnetic impurities.With increasing V doping,the antiferromagnetic interactions intensify,weakening the coupling between the local moments and conduction electrons,which in turn lowers the Kondo temperature(TK).Furthermore,the anomalous Hall effect is observed in V5.73S8,with an anomalous Hall conductivity(AHC)of 50.46 W^(-1)·cm^(-1)and anomalous Hall angle of 0.73%at 2 K.Our findings offer valuable insights into the mechanisms of the Kondo effect and anomalous Hall effect in self-intercalated transition metal chalcogenides with complex magnetism and electronic correlation effects.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 62488201 and 1240041502)the China Postdoctoral Science Foundation (Grant No. 2024T170990)+2 种基金the National Key R&D Program of China (Grant No. 2022YFA1204100)the Chinese Academy of Sciences (Grant No. XDB33030100)the Innovation Program of Quantum Science and Technology (Grant No. 2021ZD0302700)。
文摘Ising superconductivity, induced by the strong spin–orbit coupling(SOC) and inversion symmetry breaking, can lead to the in-plane upper critical field exceeding the Pauli limit and hold significant potential for advancing the study of topological superconductivity. However, the enhancement of Ising superconductivity is still a challenging problem, important for engineering Majorana fermions and exploring topological quantum computing. In this study, we investigated the superconducting properties of a series of van der Waals NbSe_(2-x)Te_(x) nanosheets. The Ising superconductivity in NbSe_(2-x)Te_(x) nanosheets can be significantly enhanced by the substitution of Te, an element with strong SOC. The fitted in-plane upper critical field of Nb Se_(1.5)Te_(0.5) nanosheets at absolute zero temperature reaches up to 3.2 times the Pauli limit. Angular dependence of magnetoresistance measurements reveals a distinct two-fold rotational symmetry in the superconducting transition region, highlighting the role of strong SOC. In addition, the fitting results of the Berezinskii–Kosterlitz–Thouless(BKT) transition and the two-dimensional(2D) Tinkham formula provide strong evidence for 2D superconductivity. These findings offer new perspectives for the design and modulation of the Ising superconducting state and pave the way for their potential applications in topological superconductivity and quantum technologies.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62488201 and 1240041502)the Ministry of Science and Technology of China(Grant No.2022YFA1204100)+1 种基金the Chinese Academy of Sciences(Grant No.XDB33030100)the Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘Two-dimensional van der Waals(vdW)magnetic materials,characterized by their tunable magnetism,spin transport properties,and remarkable quantum effects,provide significant promise for the development of efficient,low-power spintronic devices.Intriguingly,the rare earth tritelluride(RTe3)materials have attracted great attention due to their unique magnetic structure,exotic electronic properties,multiple charge density wave(CDW),and superconductivity under pressure.Here,we report the successful synthesis of high-quality DyTe_(3)single crystals using a self-flux method.DyTe_(3)shows an antiferromagnetic transition at 4.5 K and demonstrates the magnetic field-induced ferromagnetism.The high-quality DyTe_(3)single crystal demonstrates outstanding transport properties,featuring a high carrier mobility of approximately1.4×10^(4)cm^(2)·V^(-1)·s^(-1)and large linear magnetoresistance of 1300%.Furthermore,distinct Shubnikov-de Haas(SdH)oscillations are observed in DyTe_(3),revealing a small Fermi pocket and an effective mass of 0.24 me.Remarkably,the unconventional in-plane negative magnetoresistances appear along the a-axis below 2 T and c-axis until 9 T from 2 K to17 K,which are attributed to the complex helimagnetic structures caused by CDW coupling and weak single-ion anisotropy.Our findings offer a significant platform for understanding the complex magnetoresistance behavior and quantum transport effects in RTe3-type materials,holding great promise for advancing applications in electronic and spintronic devices.
基金Project supported by the Beijing Natural Science Foundation (Grant No. JQ21019)the National Key Research and Development Program of China (Grant Nos. 2022YFA1604200 and 2022YFA1204100)the Fund from Beijing Municipal Commission of Science and Technology (Grant No. Z231100006623006)。
文摘Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of Bi_(4)Br_(4) are limited, and its broadband absorption capabilities have not been validated. This study presents the first preparation of Bi_(4)Br_(4) samples using the chemical vapor transport method, resulting in a saturable absorber(SA) with a high modulation depth(46.23%) and low non-saturable loss(6.5%). The optical nonlinearity ranks among the best in similar studies. Additionally, this work applies Bi_(4)Br_(4)-SA for the first time in 1-μm fiber laser, developing a ring-cavity mode-locked fiber laser with a central wavelength of 1029.79 nm, a pulse duration of 442 fs, and a maximum output power of 90.83 m W. And a linear-cavity mode-locked fiber laser with a central wavelength of 1031.24 nm, a pulse duration of 511 fs, and a maximum output power of 92.81 m W is constructed. It is worth noting that the optical-to-optical conversion efficiency has reached about 11.54% and 33.58%.This study verifies Bi_(4)Br_(4)-SA's modulation effectiveness for 1-μm pulse lasers and provides a powerful reference for the design of high-efficiency fiber lasers.
基金The work is supported by the National Key Research and Development Program of China(Grant No.2022YFA1204104)the National Natural Science Foundation of China(Grant No.61888102)the Chinese Academy of Sciences(Grant Nos.ZDBS-SSW-WHC001 and XDB33030100).
文摘Two-dimensional(2D)magnet/superconductor heterostructures can promote the design of artificial materials for exploring 2D physics and device applications by exotic proximity effects.However,plagued by the low Curie temperature and instability in air,it is hard to realize practical applications for the reported layered magnetic materials at present.In this paper,we developed a space-confined chemical vapor deposition method to synthesize ultrathin air-stable ε-Fe_(2)O_(3) nanosheets with Curie temperature above 350 K.The ε-Fe_(2)O_(3)/NbSe_(2) heterojunction was constructed to study the magnetic proximity effect on the superconductivity of the NbSe_(2) multilayer.The electrical transport results show that the subtle proximity effect can modulate the interfacial spin–orbit interaction while undegrading the superconducting critical parameters.Our work paves the way to construct 2D heterojunctions with ultrathin nonlayered materials and layered van der Waals(vdW)materials for exploring new physical phenomena.
