Realistic Rashba and Dressehaus spin-orbit coupling for neutral atoms

TL;DR

This paper introduces a new atom-laser coupling scheme to realize spin-orbit coupling in ultra-cold neutral atoms, enabling controllable Rashba and Dresselhaus interactions with realistic experimental considerations.

Contribution

It presents a novel scheme using cyclically coupled states to generate approximate Rashba and Dresselhaus spin-orbit couplings in cold atoms, including implementation details and limitations.

Findings

Scheme achieves degenerate pseudospin states immune to decay

Four-level scheme allows controllable Dresselhaus contribution

Approximate Rashba Hamiltonian applicable with intense laser fields

Abstract

We describe a new class of atom-laser coupling schemes which lead to spin-orbit coupled Hamiltonians for ultra-cold neutral atoms. By properly setting the optical phases, a pair of degenerate pseudospin states emerge as the lowest energy states in the spectrum, and are thus immune to collisionally induced decay. These schemes use $N$ cyclically coupled ground or metastable internal states. We specialize to two situations: a three level case giving fixed Rashba coupling, and a four-level case that adds a controllable Dresselhaus contribution. We describe an implementation of the four level scheme for $\Rb87$ and analyze the sensitivity of our approach to realistic experimental limitations and imperfections. Lastly, we argue that no laser coupling scheme can give pure Rashba or Dresselhaus coupling: akin to condensed matter systems, higher order terms spoil the symmetry of these couplings. However, for sufficiently intense laser fields the continuous rotational symmetry approximately holds, making the Rashba Hamiltonian applicable for cold atoms.