Quantum Tricriticality and Phase Transitions in Spin-Orbit Coupled Bose-Einstein Condensates

Abstract

We consider a spin-orbit coupled configuration of spin-1/2 interacting bosons with equal Rashba and Dresselhaus couplings. The phase diagram of the system at T=0 is discussed with special emphasis on the role of the interaction treated in the mean-field approximation. For a critical value of the density and of the Raman coupling we predict the occurrence of a characteristic tricritical point separating the spin mixed, the phase separated, and the zero momentum states of the Bose gas. The corresponding quantum phases are investigated analyzing the momentum distribution, the longitudinal and transverse spin polarization, and the emergence of density fringes. The effect of harmonic trapping as well as the role of the breaking of spin symmetry in the interaction Hamiltonian are also discussed.

Tunneling-assisted spin-orbit coupling in bilayer Bose-Einstein condensates

“…During the last few years these topics have gained an increasing interest for ultracold atomic gases [4][5][6][7][8] which represent the systems simulating many condensed matter phenomena. Recent experimental progress in the spin-orbit coupling (SOC) of degenerate atomic gases [9][10][11][12][13] has stimulated the theoretical studies of diverse new phases due to the SOC [8,[14][15][16][17], such as emergence of the stripe phase in atomic Bose-Einstein condensates (BECs) [18][19][20][21][22], or formation of unconventional bound states [23][24][25][26] and topological superfluidity [27] for atomic fermions. It was demonstrated that for the spin-orbit (SO) coupled BECs, the half-vortex (meron) ground states may develop in harmonic traps [28][29][30][31][32].…”

Bright solitons in a two-dimensional spin-orbit-coupled dipolar Bose-Einstein condensate

“…This achievement has ignited tremendous interest in this field because of the dramatic change in the single particle dispersion (induced by spin-orbit coupling) which in conjunction with the interaction leads to many exotic superfluids [35][36][37][38][39][40][41][42][43][44][45](also see [46][47][48][49][50][51][52][53] for review). Such change in dispersion also results in exotic solitons even when the interaction is contact (without dipole-dipole interactions), including 1D bright solitons [54][55][56][57][58][59][60] for a BEC with attractive contact interactions, 1D dark [61,62] and gap solitons [63][64][65] for a BEC with repulsive contact interactions, as well as 1D dark solitons for Fermi superfluids [66,67].…”

A stripe phase with supersolid properties in spin–orbit-coupled Bose–Einstein condensates

“…With ultracold atoms, idealized Hamiltonians can be experimentally realized and studied. Starting from superfluid Bose-Einstein condensates (BECs), several forms of supersolid have been predicted by adding interactions in the form of dipolar interactions 12,13 , Rydberg interactions 14 , superradiant Rayleigh scattering 15 , nearest-neighbour interaction in lattices 16 and spin-orbit interactions [5][6][7][8] . Several of these proposals lead to solidity along a single spatial direction maintaining their gaseous or liquid-like properties along the other directions i .…”

“…In the present case, the periodicity is given by the wavelength and geometry of the Raman beams. It is then further modified by the spin gap parameter  and the interatomic interactions 5,6 to be 2d /   2 1/ F   , where F = (2Er + n(g+ iii Since the tunnel coupling along the superlattice direction is weak (about 1 kHz) it seems possible that the alignment of moving stripe patterns is more sensitive to perturbations than for stationary stripes and leads to a reduced Debye-Waller factor for moving stripes. g))/4.…”