Symmetry breaking and phase transitions in Bose-Einstein condensates with spin-orbital-angular-momentum coupling

TL;DR

This theoretical study explores how spinor Bose-Einstein condensates with spin-orbital-angular-momentum coupling exhibit various quantum phases and phase transitions, including vortex-molecule states, depending on atom-light coupling strength.

Contribution

It introduces the concept of vortex-molecule phases in spinor BECs and analyzes their role in continuous phase transitions, expanding understanding of symmetry-breaking phenomena.

Findings

Identification of multiple quantum phases including vortex-molecule states

Analysis of phase transitions driven by atom-light coupling strength

Predictions testable in current cold-atom experiments

Abstract

Theoretical study is presented for a spinor Bose-Einstein condensate, whose two components are coupled by copropagating Raman beams with different orbital angular momenta. The investigation is focused on the behavior of the ground state of this condensate, depending on the atom-light coupling strength. By analyzing the ground state, we have identified a number of quantum phases, which reflect the symmetries of the effective Hamiltonian and are characterized by the specific structure of the wave function. In addition to the well-known stripe, polarized and zero-momentum phases, our results show that the system can support phases, whose wave function contains a complex vortex molecule. Such molecule plays an important role in the continuous phase transitions of the system. The predicted behavior of vortex-molecule phases can be examined in cold-atom experiments using currently existing techniques.