Experiments with synthetic spin-orbit coupling and spin transport in Bose Einstein Condensates

Robert John Niffenegger, Purdue University


In this thesis I will describe my experiments to study spin transport of spin Bose Einstein Condensates (BECs) with synthetic spin-orbit coupling. First I will describe procedures used to reproduce previous experiments with synthetic gauge fields in Bose-Einstein Condensates, from constant vector potentials to synthetic electric fields and synthetic spin-orbit coupling as well as all of the necessary calibration experiments. Next I will describe new experiments measuring spin transport induced by synthetic spin-dependent electric fields in spin-orbit coupled Bose-Einstein Condensates (BECs). The one dimensional (1D) spin-orbit coupling (SOC) is created with counter propagating Raman lasers which couple hyperfine sub-levels and momentum states of 87Rb, allowing us to engineer spin dependent vector potentials. Quickly lowering the Raman laser intensity, decreases the spin-orbit Raman coupling strength (Ω), separates the spin vector potentials and applies opposite synthetic electric fields to the two dressed spin BECs. We allow them to oscillate in opposite directions within the optical trap (exhibiting a spin dipole mode) and measure the time evolution of their momentum and density after time-of-flight (TOF). The damping of the oscillations as the spin BECs collide is found to drastically increase for larger final Raman coupling. Over longer time scales, the bare spins' oscillations damp and thermalize. However, with Raman coupling, dressed spins' oscillations are overdamped and accompanied by rich excitations in the BEC but less thermalization.




Chen, Purdue University.

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