Symmetry classification of spin-orbit coupled spinor Bose-Einstein condensates

TL;DR

This paper develops a symmetry classification scheme for spin-orbit coupled spinor Bose-Einstein condensates, revealing various lattice structures and a unique time-reversal invariant many-body ground state.

Contribution

It introduces a novel symmetry classification method for ground states of spinor BECs with spin-orbit coupling, identifying new lattice structures and a fragmented ground state.

Findings

Emergence of kagome and nematic vortex lattices without external lattice potential.

Existence of a time-reversal invariant many-body ground state in pseudo spin-1/2 condensates.

Broken continuous SO(2) symmetry into discrete cyclic groups.

Abstract

We develop a symmetry classification scheme to find ground states of pseudo spin-1/2, spin-1, and spin-2 spin-orbit coupled spinor Bose-Einstein condensates, and show that as the SO(2) symmetry of simultaneous spin and space rotations is broken into discrete cyclic groups, various types of lattice structures emerge in the absence of a lattice potential, examples include two different kagaome lattices for pseudo spin-1/2 condensates and a nematic vortex lattice in which uniaxial and biaxial spin textures align alternatively for spin-2 condensates. For the pseudo spin-1/2 system, although mean-field states always break time-reversal symmetry, there exists a time-reversal invariant many-body ground state, which is fragmented and expected to be observed in a micro-condensate.