Theory of topological superconductivity and antiferromagnetic correlated insulators in twisted bilayer WSe2
Chuyi Tuo, Ming-Rui Li, Zhengzhi Wu, Wen Sun, Hong Yao
Abstract
Abstract Since the very recent discovery of unconventional superconductivity in twisted WSe 2 homobilayers at filling ν = − 1, considerable interest has arisen in revealing its mechanism. In this paper, we developed a three-band tight-binding model with non-trivial band topology by direct Wannierization of the low-energy continuum model. Incorporating both onsite Hubbard repulsion and next-nearest-neighbor attraction, we then performed a mean-field analysis of the microscopic model and obtained a phase diagram qualitatively consistent with the experiment results. For zero or weak displacement field, the ground state is a Chern number C = ± 2 topological superconductor in the Altland-Zirnbauer A-class (breaking time-reversal but preserving total S z symmetry) with inter-valley pairing dominant in $${d}_{xy}\pm i{d}_{{x}^{2}-{y}^{2}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>x</mml:mi> <mml:mi>y</mml:mi> </mml:mrow> </mml:msub> <mml:mo>±</mml:mo> <mml:mi>i</mml:mi> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi>x</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>−</mml:mo> <mml:msup> <mml:mrow> <mml:mi>y</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:msub> </mml:math> –wave (mixing with a subdominant p x ∓ i p y -wave) component. For a relatively strong displacement field, the ground state is a correlated insulator with the 120° antiferromagnetic order. Our results provide new insights into the nature of the twisted WSe 2 systems and suggest the need for further theoretical and experimental explorations.