The REAgSb_(2)(RE = rare earth and Y) family has drawn considerable research interest because the two-dimensional Sb net in their crystal structures hosts topological fermions and hence rich topological properties. We...The REAgSb_(2)(RE = rare earth and Y) family has drawn considerable research interest because the two-dimensional Sb net in their crystal structures hosts topological fermions and hence rich topological properties. We report herein the magnetization and magnetotransport measurements of SmAgSb_(2) single crystal, which unveil very large magnetoresistance and high carrier mobility up to 6.2 × 10^(3)% and 5.58 × 10^(3)cm^(2)·V^(-1)·s^(-1), respectively. The analysis of both Shubnikov–de Haas and de Haas–van Alphen quantum oscillations indicates nontrivial Berry phases in the paramagnetic state while trivial Berry curvature in the antiferromagnetic state, indicating a topological phase transition induced by the antiferromagnetic order. It is also supported by the first-principles calculations. The results not only provide a new interesting topological material but also offer valuable insights into the correlation between magnetism and nontrivial topological states.展开更多
Nb_(2)S_(2)C is a van der Waals type layered superconductor with a transition temperature Tc=7.6 K.In this paper,detailed calculations of the electronic structure and topological properties of Nb_(2)S_(2)C were perfor...Nb_(2)S_(2)C is a van der Waals type layered superconductor with a transition temperature Tc=7.6 K.In this paper,detailed calculations of the electronic structure and topological properties of Nb_(2)S_(2)C were performed from first principles.We find that Nb2S2C is a highly anisotropic metal with multi-band characteristics.In the absence of spin-orbit coupling(SOC),there appears one pair of triply degenerate points created by band inversion along the Γ-A line.When SOC is considered,the triple points are gapped.Intriguingly,two distinct types of topological states,including topological Dirac semimetal and topological insulator states,co-emergence in the vicinity of Fermi level.Moreover,the topology of Nb_(2)S_(2)C is robust to external pressure and the Fermi level can be shifted downward to the topological Dirac semimetal state and topological insulator state at 10 GPa and 14 GPa,respectively.The results herein provide a new platform not only for the studies of physics of low-dimensional superconductor but also for further investigations of topological superconductivity.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12004405,12334008,and 12374148)the Double First-Class Initiative Fund of Shanghai Tech University+2 种基金the Analytical Instrumentation Center of Shanghai Tech University(Grant No.SPST-AIC10112914)the research fund from the Shanghai Sailing Program(Grant No.23YF1426900)the fund from the National Key R&D Program of China(Grant Nos.2022YFA1402702 and 2021YFA1401600)。
文摘The REAgSb_(2)(RE = rare earth and Y) family has drawn considerable research interest because the two-dimensional Sb net in their crystal structures hosts topological fermions and hence rich topological properties. We report herein the magnetization and magnetotransport measurements of SmAgSb_(2) single crystal, which unveil very large magnetoresistance and high carrier mobility up to 6.2 × 10^(3)% and 5.58 × 10^(3)cm^(2)·V^(-1)·s^(-1), respectively. The analysis of both Shubnikov–de Haas and de Haas–van Alphen quantum oscillations indicates nontrivial Berry phases in the paramagnetic state while trivial Berry curvature in the antiferromagnetic state, indicating a topological phase transition induced by the antiferromagnetic order. It is also supported by the first-principles calculations. The results not only provide a new interesting topological material but also offer valuable insights into the correlation between magnetism and nontrivial topological states.
基金supported by the Natural Science Foundation of China (Grant No. 52073075)Shenzhen Science and Technology Program (Grant No. KQTD20170809110344233)Science and Technology Innovation Talents Program of Henan Province (Grant No. 174200510010)。
文摘Nb_(2)S_(2)C is a van der Waals type layered superconductor with a transition temperature Tc=7.6 K.In this paper,detailed calculations of the electronic structure and topological properties of Nb_(2)S_(2)C were performed from first principles.We find that Nb2S2C is a highly anisotropic metal with multi-band characteristics.In the absence of spin-orbit coupling(SOC),there appears one pair of triply degenerate points created by band inversion along the Γ-A line.When SOC is considered,the triple points are gapped.Intriguingly,two distinct types of topological states,including topological Dirac semimetal and topological insulator states,co-emergence in the vicinity of Fermi level.Moreover,the topology of Nb_(2)S_(2)C is robust to external pressure and the Fermi level can be shifted downward to the topological Dirac semimetal state and topological insulator state at 10 GPa and 14 GPa,respectively.The results herein provide a new platform not only for the studies of physics of low-dimensional superconductor but also for further investigations of topological superconductivity.
