Valley-based topological phases offer a wealth of exotic quantum states with tunable functionalities, driven by the valley degree of freedom. In this work, by constructing heterostructures of germanene (silicene, stanene) on various magnetic substrates, we address key tuning factors such as the spin-orbit coupling (SOC) strength of the substrate, magnetic orientations, and stacking orders, all of which govern multiple valley-based topological features. We present a comprehensive guiding principle for the efficient manipulation of these features, achieved simply by designing and modulating the magnetic properties of the underlying substrates. Specifically, increasing the SOC strength of the magnetic substrate acilitates a range of topological phase transitions characterized by different Chern numbers, with many systems exhibiting a transition from quantum valley Hall to quantum anomalous Hall (QAH) states. Additionally, rotating the in-plane magnetic orientation of the substrate enables tunability of the Chern number and chirality, within a moderate range of SOC strength. Furthermore, the antiferromagnetic coupling of the magnetic substrate can induce valley-based QAH states with substantial valley gaps, leveraging its high Curie temperature (TC) to enable the realization of multiple tunable magnetic topologies at elevated temperatures. Our findings provide a straightforward strategy for the design and manipulation of spintronic and valleytronic devices that can potentially operate under high-temperature conditions.
Valley relaxation of resident electrons and holes in a monolayer semiconductor: Dependence on carrier density and the role of substrate-induced disorder
Floquet-engineered Valley Topology with Anisotropic Response in 1T'-WSe$_2$ and Janus WSeTe monolayers
Beijing National Research Center for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所，北京凝聚态物理国家研究中心）；University of Chinese Academy of Sciences（中国科学院大学）；Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (Ministry of Education), School of Physics, Beijing Institute of Technology（北京理工大学物理学院，先进光电量子结构及测量教育部重点实验室，量子物理中心）；Department of Physics and Center of Quantum Materials and Devices, College of Physics, Chongqing University（重庆大学物理学院，量子材料与器件中心，物理学系）；Chongqing Key Laboratory for Strongly Coupled Physics, Chongqing University（重庆大学强耦合物理重庆市重点实验室）；Songshan Lake Materials Laboratory（松山湖材料实验室）
Large-Gap Quantum Spin Hall States in Stanene Grown on Substrate
二维锡烯是实现室温量子自旋霍尔（QSH）效应的理想材料。近年来，人们利用分子束外延技术制备了单层锡烯，但在Bi $_2$ Te $_3$（111）衬底上显示出金属特征，这促使我们研究衬底的重要影响。基于第一性原理计算，我们发现，不同的衬底条件显着调谐锡烯的电子性质。支持的锡烯给出平凡或QSH状态，与显着的Rashba分裂引起的反转不对称性。更重要的是，大的间隙（高达0.3 eV）的QSH状态是可实现的，当锡烯生长在各种基板上，如SrTe，PbTe，BaSe和BaTe的阴离子终止（111）表面。这些发现对进一步研究锡烯和大能隙QSH态具有重要的指导意义。
Multiple magnetic states, valley electronics, and topological phase transitions in two-dimensional Janus XYZH (X = Sc, Y, La, Y = Cl, Br, I, and Z = S, Se, Te): From monolayers to bilayers
