Magnetic-field-induced Fabry-Perot resonances in helical edge states

Abstract

We study electronic transport across a helical edge state exposed to a uniform magnetic (⃗B) field over a finite length. We show that this system exhibits Fabry-Pérot-type resonances in electronic transport. The intrinsic spin anisotropy of the helical edge states allows us to tune these resonances by changing the direction of the ⃗B field while keeping its magnitude constant. This is in sharp contrast to the case of nonhelical one-dimensional electron gases with a parabolic dispersion, where similar resonances do appear in individual spin channels (↑ and ↓) separately which, however, cannot be tuned by merely changing the direction of the ⃗B field. These resonances provide a unique way to probe the helical nature of the theory. We study the robustness of these resonances against a possible static impurity in the channel.