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.
Highlights
Spin-orbit (SO) coupling is essential for realizing topological insulators, noninteracting fermionic systems with topological order [1,2], and yet in other contexts it leads to parasitic effects such as reduced spin coherence times [3]
We describe a new class of atom-laser coupling schemes which lead to spin-orbit-coupled Hamiltonians for ultracold neutral atoms
We argue that the Rashba Hamiltonian applies only in the large intensity limit since any laser coupling scheme will produce terms nonlinear in momentum that decline with intensity
Summary
Spin-orbit (SO) coupling is essential for realizing topological insulators, noninteracting fermionic systems with topological order [1,2], and yet in other contexts it leads to parasitic effects such as reduced spin coherence times [3]. Realistic Rashba and Dresselhaus spin-orbit coupling for neutral atoms These schemes use N cyclically coupled ground or metastable internal states.
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