Stability of ultracold atomic Bose condensates with Rashba spin-orbit coupling against quantum and thermal fluctuations

TL;DR

This paper investigates the stability of three-dimensional Bose condensates with Rashba spin-orbit coupling, demonstrating that interactions stabilize the condensate against quantum and thermal fluctuations and characterizing the phase transition behavior.

Contribution

It provides a detailed analysis of how interactions stabilize Rashba spin-orbit coupled Bose condensates and characterizes the finite-temperature phase transition.

Findings

Quantum fluctuations cause finite depletion, ensuring stability.

Interactions stabilize the condensate at non-zero temperature.

The system transitions from condensed to normal phase at finite temperature.

Abstract

We study the stability of Bose condensates with Rashba-Dresselhaus spin-orbit coupling in three dimensions against quantum and thermal fluctuations. The ground state depletion of the plane-wave condensate due to quantum fluctuations is, as we show, finite, and therefore the condensate is stable. We also calculate the corresponding shift of the ground state energy. Although the system cannot condense in the absence of interparticle interactions, we show by estimating the number of excited particles that interactions stabilize the condensate even at non-zero temperature. Unlike in the usual Bose gas, the normal phase is not kinematically forbidden at any temperature; calculating the free energy of the normal phase at finite temperature, and comparing with the free energy of the condensed state, we infer that generally the system is condensed at zero temperature, and undergoes a transition to normal at non-zero temperature.