Stacking-dependent topological quantum states in bilayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Mn</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Cl</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Br</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

Abstract

Stacking-dependent physics is emerging as a fascinating research topic for two-dimensional materials. A variety of novel properties can be achieved by layer stacking according to different modes. However, most of the studies focus on the impact of electronic, superconducting, optical, and magnetic properties. In this work, we have systematically studied the stacking-dependent topological quantum states in bilayer ${\mathrm{Mn}}_{2}{\mathrm{Cl}}_{3}{\mathrm{Br}}_{3}$ by the first-principles electronic structure calculations. Here, ferromagnetic layer coupling is always favored in different stacking modes. Many exotic topological quantum states, such as topological nodal-ring spin-gapless semimetal state, spin-valley polarized quantum valley Hall (SVP-QVH) effect, and high Chern number quantum anomalous Hall effect can be realized in this single system. Among these states, the SVP-QVH is a new topological phase discovered for the first time, in which there are two topologically protected gapless chiral edge states that carry the same spin, localize respectively on the two polarized valleys, and propagate in opposite directions along the edges. The spin-valley polarized anomalous valley Hall effect can be further realized with electron doping or gate tuning, resulting in edge states that integrate multiple degrees of freedom of valley, spin, and charge. Our research therefore provides an idea for discovery of new topological phases and design of two-dimensional multifunctional electronic, spintronic, and topological devices.

Topics & Concepts