Noise-induced Backscattering in a Helical Quantum-spin-Hall Edge

In a 2D topological-insulator edge scalar potential disorder does not induce elastic electron backscattering, implying a quantized zero-temperature conductance. At finite temperature, electron-electron interactions generate inelastic backscattering, though the resulting conductance modification vanishes as a large power of temperature due to small scattering phase-space volume. We study a novel mechanism for conductance suppression: backscattering caused by electromagnetic noise. Noise leads to disorder potentials that fluctuate randomly in time, and can backscatter electrons inelastically without constraints faced by electron-electron interactions. We quantify the noise-induced correction to the time-averaged linear conductance under a variety of possible regimes.