Controlling spin without magnetic fields -- the Bloch-Rashba rotator

TL;DR

This paper proposes a method to control and rotate the spin of a quantum particle in a lattice using time-dependent spin-orbit coupling, enabling precise spin manipulation without magnetic fields.

Contribution

It introduces the Bloch-Rashba rotator, a novel spin control technique utilizing lattice tilting and dynamic Rashba interaction to achieve large spin rotations.

Findings

Large spin rotations achieved through successive Bloch oscillations.

Optimal time-dependent spin-orbit coupling enhances rotation efficiency.

Method enables precise spin control without magnetic fields.

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, the Bloch-Rashba rotator, without requiring an applied magnetic field.