Probing spin-orbit interactions in monolayer WTe 2 edge states

Monolayer WTe 2 displays edge conduction that is consistent with the material being a two-dimensional topological insulator. The expected helical nature of the edge conduction should limit the conductance between adjacent contacts on an edge to e 2/h, and this is consistent with experiments to date. However, the helical nature has not been supported by experiments that probe the form of the Hamiltonian of the edge states. To address this, we investigate the angular dependence of the magnetic field on the conduction of edges and cracks in monolayer WTe 2 flakes as a function of gate voltage, temperature, and edge orientation relative to the crystal axes as determined by scanning microwave impedance microscopy.