Symmetryprotected skyrmions in threedimensional spinorbitcoupled Bose gases
Abstract
We present a variational study of pseudospin1 /2 Bose gases in a harmonic trap with weak threedimensional (3D) spinorbit coupling of σ .p type. This spinorbit coupling mixes states with different parities, which inspires us to approximate the singleparticle state with the eigenstates of the total angular momentum, i.e., superposition of harmonic s wave and p wave states. As the timereversal symmetry is protected by twobody interaction, we set the variational order parameter as the combination of two mutually timereversal symmetric eigenstates of the total angular momentum. The variational results essentially reproduce the 3D skyrmionlike ground state recently identified by Kawakami et al. [T. Kawakami, T. Mizushima, M. Nitta, and K. Machida, Phys. Rev. Lett. 109, 015301 (2012), 10.1103/PhysRevLett.109.015301]. We show that these skyrmionlike ground states emerging in this model are primarily caused by the p wave spatial mode involved in the variational order parameter that drives two spin components spatially separated. We find the ground state of this system falls into two phases with different density distribution symmetries depending on the relative magnitude of intraspecies and interspecies interaction: phase I has parity symmetric and axisymmetric density distributions, while phase II is featured with special joint symmetries of discrete rotational and timereversal symmetry. With the increasing interaction strength the transition occurs between two phases with distinct density distributions, while the topological 3D skyrmionlike spin texture is symmetry protected.
 Publication:

Physical Review A
 Pub Date:
 May 2015
 DOI:
 10.1103/PhysRevA.91.053624
 arXiv:
 arXiv:1503.00128
 Bibcode:
 2015PhRvA..91e3624C
 Keywords:

 67.85.Fg;
 03.75.Mn;
 67.85.Jk;
 03.75.Lm;
 Multicomponent condensates;
 spinor condensates;
 Other BoseEinstein condensation phenomena;
 Tunneling Josephson effect BoseEinstein condensates in periodic potentials solitons vortices and topological excitations;
 Condensed Matter  Quantum Gases
 EPrint:
 7.1 pages, 3 figures