Gate tunable exciton superfluid and topological phases in van der Waals heterobilayer

Van der Waals heterostructures of 2D materials provide a powerful approach toward engineering various quantum phases of matter. In one work, we show that heterobilayers of 2D valley semiconductors can be tuned through interlayer bias between an exciton superfluid, a quantum anomalous Hall insulator, and a QSH insulator. The tunability between these distinct phases results from the competition of Coulomb interaction with the interlayer quantum tunneling that has a chiral form in valley semiconductors. In another work, we realize electrically tunable QSH insulator with large gap in van der Waals heterobilayer of monolayer transition metal dichalcogenide and hexagonal boron arsenide (BAs), in particular the WSe₂/BAs heterobilayer. Our findings point to exciting opportunities for harnessing both protected topological edge channels and bulk superfluidity in an electrically configurable platform.
[1] Q. Zhu, W.-Y. Tu, Q. Tong, W. Yao, Sci. Adv. 5, eaau6120 (2019).
[2] Q. Zhu, Q. Tong, H. Sun, Y. Wang, W. Yao, 2D Mater. 6, 045037 (2019).