论文标题
相关驱动的三倍拓扑相变，单层$ \ mathrm {osbr_2} $
Correlation-driven threefold topological phase transition in monolayer $\mathrm{OsBr_2}$
论文作者
论文摘要
自旋轨道耦合（SOC）与电子相关结合可以诱导拓扑相变，从而产生新型的电子状态。在这里，我们研究了SOC的影响与相关性效应对单层$ \ MATHRM {OSBR_2} $的物理性质的影响，基于具有广义梯度近似以及$ U $（GGA+$ U $）方法的第一原理计算。 With intrinsic out-of-plane magnetic anisotropy, $\mathrm{OsBr_2}$ undergoes threefold topological phase transition with increasing $U$, and valley-polarized quantum anomalous Hall insulator (VQAHI) to half-valley-metal (HVM) to ferrovalley insulator (FVI) to HVM to VQAHI to HVM to FVI transitions可以诱导。这些拓扑相变与标志可逆的浆果曲率和频段反转连接，$ d_ {xy} $/$ d_ {x^2-y^2} $和$ d_ {z^2} $ orbitals。由于$ \ bar {6} m2 $对称性，$ \ mathrm {osbr_2} $的压电偏振沿着平面扶手椅方向限制，只有一个$ d_ {11} $是独立的。对于给定的材料，应固定相关强度，并且$ \ mathrm {OSBR_2} $可能是Piezoelectric VQAHI（PVQAHI），Piezoelectric HVM（PHVM）或Piezoelectric FVI（PFVI）。可以通过逆转OS原子的磁化来翻转山谷极化，而Ferrovalley（FV）和非平凡拓扑特性将通过操纵平面外磁化为平面内抑制。在被认为是合理的$ U $范围内，估计的居里温度都高于室温。我们的发现对$ \ mathrm {OSBR_2} $的可能电子状态提供了全面的理解，并确认强大的SOC与电子相关性结合可以诱导多个量子相变。
Spin-orbit coupling (SOC) combined with electronic correlation can induce topological phase transition, producing novel electronic states. Here, we investigate the impact of SOC combined with correlation effects on physical properties of monolayer $\mathrm{OsBr_2}$, based on first-principles calculations with generalized gradient approximation plus $U$ (GGA+$U$) approach. With intrinsic out-of-plane magnetic anisotropy, $\mathrm{OsBr_2}$ undergoes threefold topological phase transition with increasing $U$, and valley-polarized quantum anomalous Hall insulator (VQAHI) to half-valley-metal (HVM) to ferrovalley insulator (FVI) to HVM to VQAHI to HVM to FVI transitions can be induced. These topological phase transitions are connected with sign-reversible Berry curvature and band inversion between $d_{xy}$/$d_{x^2-y^2}$ and $d_{z^2}$ orbitals. Due to $\bar{6}m2$ symmetry, piezoelectric polarization of $\mathrm{OsBr_2}$ is confined along the in-plane armchair direction, and only one $d_{11}$ is independent. For a given material, the correlation strength should be fixed, and $\mathrm{OsBr_2}$ may be a piezoelectric VQAHI (PVQAHI), piezoelectric HVM (PHVM) or piezoelectric FVI (PFVI). The valley polarization can be flipped by reversing the magnetization of Os atoms, and the ferrovalley (FV) and nontrivial topological properties will be suppressed by manipulating out-of-plane magnetization to in-plane one. In considered reasonable $U$ range, the estimated Curie temperatures all are higher than room temperature. Our findings provide a comprehensive understanding on possible electronic states of $\mathrm{OsBr_2}$, and confirm that strong SOC combined with electronic correlation can induce multiple quantum phase transition.
