Strain induced Chern insulator

Topological phase transitions are at the heart of fundamental condensed matter physics. The topological crystalline insulator (TCI) exhibits nontrivial topological properties protected by crystal symmetries as well as time-reversal symmetry. This opens up a pathway for manipulation of the topological states by breaking these symmetries. While mechanical strain can be used to break mirror and rotational symmetries, time-reversal symmetry can be broken by doping the material with a magnetic element. In this proposal, we attempt to apply uniaxial strain on the Mn-doped TCI Pb1-x-ySnxMnySe, thereby simultaneously breaking both the mirror and fourfold rotation symmetries as well as time-reversal symmetry. This is expected to result in a strain-induced phase transition from a topological crystalline insulator to a Chern insulator. Such a topological phase transition is fundamentally interesting and has not yet been observed. We will perform detailed angle-resolved photoemission spectroscopy (ARPES) measurements of the surface electronic structure with and without applied strain to elucidate the detailed nature of the proposed phase transition.

拓扑相变是凝聚态物理基础研究的核心课题。拓扑晶体绝缘体（TCI）展现出受晶体对称性与时间反演对称性共同保护的非平庸拓扑性质，这为通过打破上述对称性调控拓扑态开辟了可行路径。机械应变可用于破坏镜像与旋转对称性，而向材料中掺杂磁性元素则能够打破时间反演对称性。在本项目提案中，我们拟对锰掺杂的拓扑晶体绝缘体Pb₁₋ₓ₋ᵧSnₓMnᵧSe施加单轴应变，以此同时破坏镜像、四重旋转对称性与时间反演对称性。预期此举将诱导该材料从拓扑晶体绝缘体向陈绝缘体发生应变驱动的相变。这类拓扑相变兼具基础研究价值且迄今尚未被实验观测到。我们将通过开展施加与未施加应变条件下的角分辨光电子能谱（ARPES）测试，对样品表面电子结构进行精细表征，以阐明该拟议相变的详细物理本质。