Nonlinear Ballistic Response of Quantum Spin Hall Edge States

Topological edge states (TES) exhibit dissipationless transport, yet their dispersion has never been probed. Here we show that the nonlinear electrical response of ballistic TES ascertains the presence of symmetry breaking terms, such as deviations from nonlinearity and tilted spin quantization axes. The nonlinear response stems from discontinuities in the band occupation on either side of a Zeeman gap, and its direction is set by the spin orientation with respect to the Zeeman field. We determine the edge dispersion for several classes of TES and discuss experimental measurement.

Automated summary

Topological edge states show dissipationless transport. Nonlinear electrical response of ballistic TES confirms the presence of symmetry breaking terms, such as deviations from nonlinearity. The direction of nonlinear response is determined by the spin orientation with respect to the Zeeman field.