Interference effects induced by a precessing easy-plane magnet coupled to a helical edge state

Abstract

The interaction of a magnetic insulator with the helical electronic edge of a two-dimensional topological insulator has been shown to lead to many interesting phenomena. One of these is that for a suitable orientation of the magnetic anisotropy axis, the exchange coupling to an easy-plane magnet has no effect on DC electrical transport through a helical edge, despite the fact that it opens a gap in the spectrum of the helical edge [Meng et al., Phys. Rev. B 90, 205403 (2014)]. Here, we theoretically consider such a magnet embedded in an interferometer, consisting of a pair of helical edge states connected by two tunneling contacts, at which electrons can tunnel between the two edges. Using a scattering matrix approach, we show that the presence of the magnet in one of the interferometer arms gives rise to AC currents in response to an applied DC voltage. On the other hand, the DC Aharonov-Bohm effect is absent at zero temperature and small DC voltages, and only appears if the applied voltage or the temperature exceeds the magnet-induced excitation gap.

Signatures of Jackiw-Rebbi resonance in the thermal conductance of topological Josephson junctions with magnetic islands

“…The key role played by a magnetic island placed inside the 2DTI is to introduce a boundary with a backscattering process in the Dirac system constituted by the helical edge states. Without the superconducting ingredient, this phenomenon leads to interesting effects in the electron transport [28][29][30][31][32][33] and in thermoelectric [34][35][36] properties. The fact that the magnetic island may have multiple domains further extends the scenario to interesting topological structures.…”