Effect of Induced Spin-Orbit Coupling for Atoms via Laser Fields

We propose an experimental scheme to observe spin-orbit coupling effects of a two-dimensional Fermi atomic gas cloud by coupling its internal electronic states (pseudospins) to radiation in a Lambda configuration. The induced spin-orbit coupling can be of the Dresselhaus and Rashba type with a Zeeman term. We show that the optically induced spin-orbit coupling can lead to a spin-dependent effective mass under appropriate conditions with one of them able to be tuned between positive and negative effective masses. As a direct observable we show that in the expansion dynamics of the atomic cloud the initial atomic cloud splits into two clouds for the positive effective mass case regime, and into four clouds for the negative effective mass regime.

Figure 1

(a) Three-level $\Lambda$-type system coupled to position-dependent laser fields with large detuning. (b) Laser configuration for ${\Omega }_1$.

Figure 2

Number of atoms versus Fermi energy at $\delta m/m=1.07,1.13,1.20$, corresponding to the effective mass ${\tilde{m}}_{-}=-15m,-7.7m,-5m$.

Figure 3

Splitting of atomic cloud for the positive effective mass case (a)–(c) and negative mass case (d)–(f) after turning off the trap and laser fields. The $\times n$ label represents the value each panel has been multiplied by to keep figure to scale.