Controlling spin without magnetic fields: The Bloch-Rashba rotator

Abstract

We consider the dynamics of a quantum particle held in a lattice potential and subjected to a time-dependent spin-orbit coupling. Tilting the lattice causes the particle to perform Bloch oscillations, and by suitably changing the Rashba interaction during its motion, the spin of the particle can be gradually rotated. Even if the Rashba coupling can only be altered by a small amount, large spin rotations can be obtained by accumulating the rotation from successive oscillations. We show how the time dependence of the spin-orbit coupling can be chosen to maximize the rotation per cycle, and thus how this method can be used to produce a precise and controllable spin rotator, which we term the Bloch-Rashba rotator, without requiring an applied magnetic field.

Tunable zero modes and quantum interferences in flat-band topological insulators

“…It is, however, a more natural TR transformation if we consider the two legs of the ladder as the up and down components of a spin-1/2 particle, something we can do if we take c ( †) n,α to be fermionic operators. This approach has been explored in [34,38,80,96,111]. However, a fermionic TR symmetry usually squares to −1, not 1 as is the case, so it is still non-conventional in that regard.…”