We investigate the electronic structure of NbGeSb with non-symmorphic symmetry.We employ angle-resolved photoemission spectroscopy(ARPES)to observe and identify the bulk and surface states over the Brillouin zone.By u...We investigate the electronic structure of NbGeSb with non-symmorphic symmetry.We employ angle-resolved photoemission spectroscopy(ARPES)to observe and identify the bulk and surface states over the Brillouin zone.By utilizing high-energy photons,we identify the bulk Fermi surface and bulk nodal line along the direction X–R,while the Fermi surface of the surface state is observed by using low-energy photons.We observe the splitting of surface bands away from the high-symmetry point X.The density functional theory calculations on bulk and 1 to 5-layer slab models,as well as spin textures of NbGeSb,verify that the band splitting could be attributed to the Rashba-like spin–orbit coupling caused by space-inversion-symmetry breaking at the surface.These splitted surface bands cross with each other,forming two-dimensional Weyl-like crossings that are protected by mirror symmetry.Our findings provide insights into the two-dimensional topological and symmetry-protected band inversion of surface states.展开更多
We conduct a detailed examination of the magnetic and electrical transport properties in GdAlSi and SmAlGe crystals,which possess a LaPtSi-type structure(space group I4_(1)md).The magnetic susceptibility data unambigu...We conduct a detailed examination of the magnetic and electrical transport properties in GdAlSi and SmAlGe crystals,which possess a LaPtSi-type structure(space group I4_(1)md).The magnetic susceptibility data unambiguously reveal magnetic ordering below a characteristic transition temperature(T_(N)).For GdAlSi,a hysteresis loop is observed in the magnetization and magnetoresistance curves within the ab plane when the magnetic field is applied below T_(N),which is around32 K.Notable specific heat anomalies are detected at 32 K for GdAlSi and 6 K for SmAlGe,confirming the occurrence of magnetic transitions.In addition,the extracted magnetic entropy at high temperatures is consistent with the theoretical value of Rln(2J+1) for J=7/2 in Gd^(3+) and J=5/2 in Sm^(3+),respectively.SmAlGe also exhibits Schottky-like specific heat contributions.Additionally,both GdAlSi and SmAlGe exhibit positive magnetoresistance and a normal Hall effect.展开更多
We report the magnetotransport and thermal properties of RuAs_(2) single crystal.RuAs_(2) exhibits semiconductor behavior and localization effect.The crossover from normal state to diffusive transport in the weak loca...We report the magnetotransport and thermal properties of RuAs_(2) single crystal.RuAs_(2) exhibits semiconductor behavior and localization effect.The crossover from normal state to diffusive transport in the weak localization(WL)state and then to variable range hopping(VRH)transport in the strong localization state has been observed.The transitions can be reflected in the measurement of resistivity and Seebeck coefficient.Negative magnetoresistance(NMR)emerges with the appearance of localization effect and is gradually suppressed in high magnetic field.The temperature dependent phase coherence length extracted from the fittings of NMR also indicates the transition from WL to VRH.The measurement of Hall effect reveals an anomaly of temperature dependent carrier concentration caused by localization effect.Our findings show that RuAs_(2) is a suitable platform to study the localized state.展开更多
Magnetic materials with noncollinear spin configurations have engendered significant interest in condensed matter physics due to their intriguing physical properties.We direct our attention towards the magnetic proper...Magnetic materials with noncollinear spin configurations have engendered significant interest in condensed matter physics due to their intriguing physical properties.We direct our attention towards the magnetic properties and critical behavior of single-crystal SmMn_(2)Ge_(2),an itinerant magnet with numerous temperature-dependent magnetic phase transitions.Notably,SmMn_(2)Ge_(2)displays significant magnetic anisotropy with easy magnetization direction switching from the c axis to the ab plane as temperature decreases.The critical behavior of the ferromagnetic transition occurring above room temperature is thoroughly examined.Reliable and self-consistent critical exponents,includingβ=0.292(2),γ=0.924(8),andδ=4.164(6),along with the Curie temperature T_c=347 K,are extracted through various methods,which provide evidence for the coexistence of multiple magnetic interactions in SmMn_(2)Ge_(2).Further analysis reveals that the magnetic interaction of SmMn_(2)Ge_(2)is a long-range type with the interaction distance decaying as J(r)~r^(-4.35).展开更多
One of the greatest triumph of condensed matter physics in the past ten years is the classification of materials by the principle of topology.The existence of topological protected dissipationless surface state makes ...One of the greatest triumph of condensed matter physics in the past ten years is the classification of materials by the principle of topology.The existence of topological protected dissipationless surface state makes topological insulators great potential for applications and hotly studied.However,compared with the prosperity of strong topological insulators,theoretical predicted candidate materials and experimental confirmation of weak topological insulators(WTIs) are both extremely rare.By combining systematic first-principles calculation and angle-resolved photoemission spectroscopy measurements,we have studied the electronic structure of the dark surface of the WTI candidate Zintl Ba_(3)Cd_(2)Sb_(4)and another related material Ba_(3)Cd_(2)As_(4).The existence of two Dirac surface states on specific side surfaces predicted by theoretical calculations and the observed two band inversions in the Brillouin zone give strong evidence to prove that the Ba_(3)Cd_(2)Sb_(4)is a WTI.The spectroscopic characterization of this Zintl Ba_(3)Cd_(2)N_(4)(N = As and Sb) family materials will facilitate applications of their novel topological properties.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1403803)H.M.is supported by the Fundamental Research Funds for the Central Universities,and the Research Funds of Renmin University of China(Grant No.22XNH099)+7 种基金The results of DFT calculations described in this paper are supported by HPC Cluster of ITP-CAS.M.L.is supported by the National Natural Science Foundation of China(Grant No.12204536)the Fundamental Research Funds for the Central Universities,and the Research Funds of People’s Public Security University of China(PPSUC)(Grant No.2023JKF02ZK09)T.L.X.is supported by the National Key R&D Program of China(Grant No.2019YFA0308602)the National Natural Science Foundation of China(Grant Nos.12074425 and 11874422)Y.Y.W.is supported by the National Natural Science Foundation of China(Grant No.12104011)H.Y.L.is supported by the National Natural Science Foundation of China(Grant No.12074213)the Major Basic Program of Natural Science Foundation of Shandong Province(Grant No.ZR2021ZD01)the Project of Introduction and Cultivation for Young Innovative Talents in Colleges and Universities of Shandong Province.
文摘We investigate the electronic structure of NbGeSb with non-symmorphic symmetry.We employ angle-resolved photoemission spectroscopy(ARPES)to observe and identify the bulk and surface states over the Brillouin zone.By utilizing high-energy photons,we identify the bulk Fermi surface and bulk nodal line along the direction X–R,while the Fermi surface of the surface state is observed by using low-energy photons.We observe the splitting of surface bands away from the high-symmetry point X.The density functional theory calculations on bulk and 1 to 5-layer slab models,as well as spin textures of NbGeSb,verify that the band splitting could be attributed to the Rashba-like spin–orbit coupling caused by space-inversion-symmetry breaking at the surface.These splitted surface bands cross with each other,forming two-dimensional Weyl-like crossings that are protected by mirror symmetry.Our findings provide insights into the two-dimensional topological and symmetry-protected band inversion of surface states.
基金supported by the National Natural Science Foundation of China(Grant No.12074425)the National Key R&D Program of China(Grant No.2019YFA0308602)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China(Grant No.23XNKJ22)。
文摘We conduct a detailed examination of the magnetic and electrical transport properties in GdAlSi and SmAlGe crystals,which possess a LaPtSi-type structure(space group I4_(1)md).The magnetic susceptibility data unambiguously reveal magnetic ordering below a characteristic transition temperature(T_(N)).For GdAlSi,a hysteresis loop is observed in the magnetization and magnetoresistance curves within the ab plane when the magnetic field is applied below T_(N),which is around32 K.Notable specific heat anomalies are detected at 32 K for GdAlSi and 6 K for SmAlGe,confirming the occurrence of magnetic transitions.In addition,the extracted magnetic entropy at high temperatures is consistent with the theoretical value of Rln(2J+1) for J=7/2 in Gd^(3+) and J=5/2 in Sm^(3+),respectively.SmAlGe also exhibits Schottky-like specific heat contributions.Additionally,both GdAlSi and SmAlGe exhibit positive magnetoresistance and a normal Hall effect.
基金Project supported by the National Key Research and Development Program of China (Grant Nos.2023YFA1406500 and 2019YFA0308602)the National Natural Science Foundation of China (Grant Nos.12104011,12274388,12074425,52102333,12104010,12204004,and 11874422)the Natural Science Foundation of Anhui Province (Grant Nos.2108085QA22 and 2108085MA16)。
文摘We report the magnetotransport and thermal properties of RuAs_(2) single crystal.RuAs_(2) exhibits semiconductor behavior and localization effect.The crossover from normal state to diffusive transport in the weak localization(WL)state and then to variable range hopping(VRH)transport in the strong localization state has been observed.The transitions can be reflected in the measurement of resistivity and Seebeck coefficient.Negative magnetoresistance(NMR)emerges with the appearance of localization effect and is gradually suppressed in high magnetic field.The temperature dependent phase coherence length extracted from the fittings of NMR also indicates the transition from WL to VRH.The measurement of Hall effect reveals an anomaly of temperature dependent carrier concentration caused by localization effect.Our findings show that RuAs_(2) is a suitable platform to study the localized state.
基金the National Natural Science Foundation of China(Grant Nos.12074425 and 11874422)the National Key R&D Program of China(Grant No.2019YFA0308602)。
文摘Magnetic materials with noncollinear spin configurations have engendered significant interest in condensed matter physics due to their intriguing physical properties.We direct our attention towards the magnetic properties and critical behavior of single-crystal SmMn_(2)Ge_(2),an itinerant magnet with numerous temperature-dependent magnetic phase transitions.Notably,SmMn_(2)Ge_(2)displays significant magnetic anisotropy with easy magnetization direction switching from the c axis to the ab plane as temperature decreases.The critical behavior of the ferromagnetic transition occurring above room temperature is thoroughly examined.Reliable and self-consistent critical exponents,includingβ=0.292(2),γ=0.924(8),andδ=4.164(6),along with the Curie temperature T_c=347 K,are extracted through various methods,which provide evidence for the coexistence of multiple magnetic interactions in SmMn_(2)Ge_(2).Further analysis reveals that the magnetic interaction of SmMn_(2)Ge_(2)is a long-range type with the interaction distance decaying as J(r)~r^(-4.35).
基金supported by the National Key R&D Program of China(Grant Nos.2022YFA1403800,2018YFA0305700,and 2019YFA0308602)the Chinese Academy of Sciences(Grant Nos.QYZDB-SSW-SLH043,XDB33000000,and XDB28000000)+2 种基金the National Natural Science Foundation of China (Grant Nos.U22A600018,U1832202,12074425,11874422,11925408,11921004,and 12188101)the Informatization Plan of Chinese Academy of Sciences (Grant No.CAS-WX2021SF-0102)the Synergetic Extreme Condition User Facility (SECUF)。
文摘One of the greatest triumph of condensed matter physics in the past ten years is the classification of materials by the principle of topology.The existence of topological protected dissipationless surface state makes topological insulators great potential for applications and hotly studied.However,compared with the prosperity of strong topological insulators,theoretical predicted candidate materials and experimental confirmation of weak topological insulators(WTIs) are both extremely rare.By combining systematic first-principles calculation and angle-resolved photoemission spectroscopy measurements,we have studied the electronic structure of the dark surface of the WTI candidate Zintl Ba_(3)Cd_(2)Sb_(4)and another related material Ba_(3)Cd_(2)As_(4).The existence of two Dirac surface states on specific side surfaces predicted by theoretical calculations and the observed two band inversions in the Brillouin zone give strong evidence to prove that the Ba_(3)Cd_(2)Sb_(4)is a WTI.The spectroscopic characterization of this Zintl Ba_(3)Cd_(2)N_(4)(N = As and Sb) family materials will facilitate applications of their novel topological properties.
