Cooperative orbital moments and edge magnetoresistance in monolayer WTe₂

Quantum Spin Hall (QSH) edge states exhibit dissipationless transport that is insensitive to the crystal structure and disorder of the sample device as long as time-reversal symmetry is preserved. Here we argue that when a magnetic field is applied, the edge states of QSH insulators become highly sensitive to bulk crystalline symmetries. In particular, we find that the QSH insulator WTe₂ can display an anisotropic edge magnetoresistance that depend, and can be controlled by the Rashba and Ising spin orbit couplings introduced due to low symmetry of the crystal structure. Strikingly, maximum edge magnetoresistance occurs when the magnetic field is applied at a canted angle θ oblique to the plane, which is in stark contrast to that found in HgCdTe QSH insulators (where magnetoresistance is maximum for out-of-plane magnetic fields) or ideal QSH insulators (where maximum magnetoresistance is expected to arise for in-plane magnetic fields). We find this behavior proceeds from an unconventional orbital contribution to the edge magnetic moment that arises from “cooperative orbital moments” due to the unique low-symmetry crystal structure of WTe₂.