By using angle-resolvea photoemission spectroscopy(ARPES) combined with the first-principies electronic structure calculations,we report the quantized states at the surface of a single crystal 2 H-TaSe_(2).We have obs...By using angle-resolvea photoemission spectroscopy(ARPES) combined with the first-principies electronic structure calculations,we report the quantized states at the surface of a single crystal 2 H-TaSe_(2).We have observed sub-bands of quantized states at the three-dimensional Brillouin zone center due to a highly dispersive band with light effective mass along k_(z) direction.The quantized sub-bands shift upward towards E_(F) while the bulk band at Γ shifts downward with the decrease of temperature across charge density wave(CDW) formation.The band shifts could be intimately related to the CDW.While neither the two-dimensional Fermi-surface nesting nor purely strong electron-phonon coupling can explain the mechanism of CDW in 2 H-TaSe_(2),our experiment may ignite the interest in understanding the CDW mechanism in this family.展开更多
Unconventional superconductivity,in particular,in noncentrosymmetric systems,has been a long-sought topic in condensed matter physics.Recently,Re-based superconductors have attracted great attention owing to the poten...Unconventional superconductivity,in particular,in noncentrosymmetric systems,has been a long-sought topic in condensed matter physics.Recently,Re-based superconductors have attracted great attention owing to the potential time-reversal symmetry breaking in their superconducting states.We report the superconducting properties of noncentrosymmetric compounds Ta_(x)Re_(1-x) with 0.1 ≤x≤0.25,and find that the superconducting transition temperature reaches a maximum of ~8 K at the optimal level x=0.15.Nevertheless,muon-spin rotation and relaxation measurements reveal no time-reversal symmetry breaking existing in its superconducting state,which is in sharp contrast to both centrosymmetric Re metal and many other noncentrosymmetric Re-based superconductors.展开更多
We report on the solid-state synthesis and the strongly anisotropic transport properties of the ternary telluride TaNi_(2)Te_(3),whose three orthogonal resistivity coefficients exhibit a large ratio of 1.4:1:2294(14:1...We report on the solid-state synthesis and the strongly anisotropic transport properties of the ternary telluride TaNi_(2)Te_(3),whose three orthogonal resistivity coefficients exhibit a large ratio of 1.4:1:2294(14:1:2303) at 300 K(2 K),thereby demonstrating its quasi-one-dimensional(q1D) electronic structure.The Kohler’ s rule in different current/field configurations shows a moderate violation.Its one dimensionality manifests itself in the needle-like shape of crystal,the large anisotropic resistivity and the flat Fermi surface normal to the chain direction.Moreover,the first-principles calculations also provide evidence for the existence of the nontrivial topological carriers in this q1D system.Our calculation demonstrates that TaNi_(2)Te_(3) is a strong topological nontrivial material with topological indices(1;1 0 1) and its nontrivial topology is also evidenced from its bulk-surface correspondence.Our study may therefore offer a new platform for engineering the topologically nontrivial phase in low-dimensional materials,in analogy to the recently discovered q1D topological TaNiTe_(5).展开更多
Tantalum pentoxide(Ta_(2)O_(5)) has attracted intensive attention due to their excellent physicochemical properties.Ta_(2)O_(5) films were synthesized via electron beam evaporation(EBE)and subsequently annealed at dif...Tantalum pentoxide(Ta_(2)O_(5)) has attracted intensive attention due to their excellent physicochemical properties.Ta_(2)O_(5) films were synthesized via electron beam evaporation(EBE)and subsequently annealed at different temperatures ranging from 300 to 900℃.X-ray diffraction(XRD)results show that amorphous Ta_(2)O_(5) thin films form from 300 to 700℃ and then a phase transition to polycrystalline β-Ta_(2)O_(5) films occurs since 900℃.The surface morphology of the Ta_(2)O_(5) films is uniform and smooth.The resulted Ta_(2)O_(5)films exhibit excellent transmittance properties for wavelengths ranging from 300 to 1100 nm.The bandgap of the Ta_(2)O_(5) films is broadened from 4.32 to 4.46 eV by annealing.The 900℃ polycrystalline film electrode has improved electrochemical stability,compared to the other amorphous counterparts.展开更多
基金National Natural Science Foundation of China(50972110,51472186)Hubei Provincial Natural Science Foundation of China(2009CDA036)Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry~~
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11774421,11774424,11574394,11774423,11822412,and 11874047)the National Key R&D Program of China(Grant Nos.2016YFA0401002,2018YFA0307000,2016YFA0300504,and 2018FYA0305800)the Fundamental Research Funds for the Central Universities,China(Grant No.2042018kf-0030)。
文摘By using angle-resolvea photoemission spectroscopy(ARPES) combined with the first-principies electronic structure calculations,we report the quantized states at the surface of a single crystal 2 H-TaSe_(2).We have observed sub-bands of quantized states at the three-dimensional Brillouin zone center due to a highly dispersive band with light effective mass along k_(z) direction.The quantized sub-bands shift upward towards E_(F) while the bulk band at Γ shifts downward with the decrease of temperature across charge density wave(CDW) formation.The band shifts could be intimately related to the CDW.While neither the two-dimensional Fermi-surface nesting nor purely strong electron-phonon coupling can explain the mechanism of CDW in 2 H-TaSe_(2),our experiment may ignite the interest in understanding the CDW mechanism in this family.
基金Supported by the National Key R&D Program of China(Grant No.2018YFA0704300)the National Natural Science Foundation of China(Grant Nos.U1732162,11974061,11704047,U1832147 and 11674054)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)。
文摘Unconventional superconductivity,in particular,in noncentrosymmetric systems,has been a long-sought topic in condensed matter physics.Recently,Re-based superconductors have attracted great attention owing to the potential time-reversal symmetry breaking in their superconducting states.We report the superconducting properties of noncentrosymmetric compounds Ta_(x)Re_(1-x) with 0.1 ≤x≤0.25,and find that the superconducting transition temperature reaches a maximum of ~8 K at the optimal level x=0.15.Nevertheless,muon-spin rotation and relaxation measurements reveal no time-reversal symmetry breaking existing in its superconducting state,which is in sharp contrast to both centrosymmetric Re metal and many other noncentrosymmetric Re-based superconductors.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 11974061, U1732162, and U1832147)the financial support from the Zhejiang Provincial Natural Science Foundation of China (Grant No. LY19A040002)+3 种基金NUPTSF (Grant Nos. NY219087 and NY220038)the financial support from the Ministry of Science and Technology in Taiwan,China under Project MOST-108-2112-M-001-049-MY2Academia Sinica for the budget of ASi MATE-109-13financial support from the start-ups at Michigan State University。
文摘We report on the solid-state synthesis and the strongly anisotropic transport properties of the ternary telluride TaNi_(2)Te_(3),whose three orthogonal resistivity coefficients exhibit a large ratio of 1.4:1:2294(14:1:2303) at 300 K(2 K),thereby demonstrating its quasi-one-dimensional(q1D) electronic structure.The Kohler’ s rule in different current/field configurations shows a moderate violation.Its one dimensionality manifests itself in the needle-like shape of crystal,the large anisotropic resistivity and the flat Fermi surface normal to the chain direction.Moreover,the first-principles calculations also provide evidence for the existence of the nontrivial topological carriers in this q1D system.Our calculation demonstrates that TaNi_(2)Te_(3) is a strong topological nontrivial material with topological indices(1;1 0 1) and its nontrivial topology is also evidenced from its bulk-surface correspondence.Our study may therefore offer a new platform for engineering the topologically nontrivial phase in low-dimensional materials,in analogy to the recently discovered q1D topological TaNiTe_(5).
基金supported by the Joint Research Funds of Department of Science&Technology of Shaanxi Province and Northwestern Polytechnical University(Grant No.2020GXLH-Z-029).
文摘Tantalum pentoxide(Ta_(2)O_(5)) has attracted intensive attention due to their excellent physicochemical properties.Ta_(2)O_(5) films were synthesized via electron beam evaporation(EBE)and subsequently annealed at different temperatures ranging from 300 to 900℃.X-ray diffraction(XRD)results show that amorphous Ta_(2)O_(5) thin films form from 300 to 700℃ and then a phase transition to polycrystalline β-Ta_(2)O_(5) films occurs since 900℃.The surface morphology of the Ta_(2)O_(5) films is uniform and smooth.The resulted Ta_(2)O_(5)films exhibit excellent transmittance properties for wavelengths ranging from 300 to 1100 nm.The bandgap of the Ta_(2)O_(5) films is broadened from 4.32 to 4.46 eV by annealing.The 900℃ polycrystalline film electrode has improved electrochemical stability,compared to the other amorphous counterparts.
