Majorana corner modes in unconventional monolayers of the 1T-PtSe2 family

Abstract: In this work, we propose that Majorana zero modes can be realized at the corners of the two-dimensional unconventional insulator. We demonstrate that 1T-PtSe2 is a symmetry indicator-free (SI-free) unconventional insulator, originating from orbital hybridization between Pt $d$ and Se $p_{x,y}$ states. The kind of SI-free unconventionality has no symmetry eigenvalue indication. Instead, it is diagnosed directly by the Wannier charge centers by using the one-dimensional Wilson loop method. The obstructed edge states exhibit strong anisotropy and large Rashba splitting. By introducing superconducting proximity and an external magnetic field, the Majorana corner modes can be obtained in the 1T-PtSe2 monolayer. In the end, we construct a two-Bernevig-Hughes-Zhang model with anisotropy to capture the Majorana physics.