Edge Dynamics in a Quantum Spin Hall State: Effects from Rashba Spin-Orbit Interaction

Abstract

We analyze the dynamics of the helical edge modes of a quantum spin Hall state in the presence of a spatially nonuniform Rashba spin-orbit (SO) interaction. A randomly fluctuating Rashba SO coupling is found to open a scattering channel which causes localization of the edge modes for a weakly screened electron-electron (e-e) interaction. A periodic modulation of the SO coupling, with a wave number commensurate with the Fermi momentum, makes the edge insulating already at intermediate strengths of the e-e interaction. We discuss implications for experiments on edge state transport in a HgTe quantum well.

Disorder effects on helical edge transport in graphene under a strong tilted magnetic field

“…Other types of disorder, such like sub-lattice exchange (parity) breaking spin-orbit coupling and time-reversal symmetrybreaking spin-orbit coupling terms are expected to yield smaller contributions. Interestingly, unlike the situation encountered in semiconducting quantum wells, 22 we find that Rashba spin-orbit coupling does not lead to backscattering, at least to leading order.…”

“…Note that, unlike the QSHE in semiconductor quantum wells for which the states at the two channels are a Kramer's pair, 22 in the present case the right and left movers can have different Fermi velocities (i.e. v R = v L ).…”

“…Therefore, it alone cannot suppress the conductance from its perfect quantized value, unlike the case of the QSHE in two-dimensional TRS topological insulators. 22,33 This is a direct consequence of the structure of 0LL orbitals in graphene, for which the sub-lattice and valley pseudo-spins are locked. Landau level mixing arising from interactions, etc, can modify this conclusion slightly, but the corrections are expected to be small and suppressed at the high magnetic fields.…”

“…[18][19][20][21] Therefore, one of the important goals of this work is to investigate the role of the SOC-induced dissipation at the edge. Indeed, in the case of semiconducting quantum wells, it is known that Rashba-like disorder SOC has been identified as one of the possible causes for backscattering, 22 . In addition, it was suggested by the authors of Ref.…”

Noninvasive probes of charge fractionalization in quantum spin Hall insulators

“…This assumption no longer holds in presence of structural inversion asymmetry and its accompanying Rashba spin-orbit interaction (SOI), which can be sizeable in HgTe quantum wells. In its simplest realization, 20 Rashba SOI rotates the spin quantization axis of a 2D TI edge. The rotation angle can be tuned by a gate acting on the QSHI, and the rotation axis varies from one edge of the device to another.…”