Unconventional Bose-Einstein condensations from spin-orbit coupling

Chinese Physics Letters (Impact Factor: 0.92). 09/2008; DOI: 10.1088/0256-307X/28/9/097102
Source: arXiv

ABSTRACT According to the "no-node" theorem, many-body ground state wavefunctions of
conventional Bose-Einstein condensations (BEC) are positive-definite, thus
time-reversal symmetry cannot be spontaneously broken. We find that
multi-component bosons with spin-orbit coupling provide an unconventional type
of BECs beyond this paradigm. We focus on the subtle case of isotropic Rashba
spin-orbit coupling and the spin-independent interaction. In the limit of the
weak confining potential, the condensate wavefunctions are frustrated at the
Hartree-Fock level due to the degeneracy of the Rashba ring. Quantum zero-point
energy selects the spin-spiral type condensate through the
"order-from-disorder" mechanism. In a strong harmonic confining trap, the
condensate spontaneously generates a half-quantum vortex combined with the
skyrmion type of spin texture. In both cases, time-reversal symmetry is
spontaneously broken. These phenomena can be realized in both cold atom systems
with artificial spin-orbit couplings generated from atom-laser interactions and
exciton condensates in semi-conductor systems.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The striped phase exhibited by a spin-$1/2$ Bose-Einstein condensate with spin-orbit coupling is characterized by the spontaneous breaking of two continuous symmetries: gauge and translational symmetry. This feature, which is peculiar of supersolids and is the consequence of interaction effects, shows up in important phenomena, like the occurrence of density fringes and of a double gapless band structure in the excitation spectrum. We propose an approach to increase significantly the contrast of fringes as well as their space separation, making their experimental detection in atomic gases a realistic perspective. The approach is based on the space separation of the two spin components into a 2D bi-layer configuration, causing the reduction of the effective interspecies interaction, and on the application of a $\pi/2$ Bragg pulse, causing the increase of the wavelength of the fringes.
    Physical Review A 09/2014; 90(4). · 2.99 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We numerically investigate the ground state, the Raman-driving dynamics and the nonlinear excitations of a realized spin-orbit-coupled Bose-Einstein condensate in a one-dimensional harmonic trap. Depending on the Raman coupling and the interatomic interactions, three ground-state phases are identified: stripe, plane wave and zero-momentum phases. A narrow parameter regime with coexistence of stripe and zero-momentum or plane wave phases in real space is found. Several sweep progresses across different phases by driving the Raman coupling linearly in time is simulated and the non-equilibrium dynamics of the system in these sweeps are studied. We find kinds of nonlinear excitations, with the particular dark solitons excited in the sweep from the stripe phase to the plane wave or zero-momentum phase within the trap. Moreover, the number and the stability of the dark solitons can be controlled in the driving, which provide a direct and easy way to generate dark solitons and study their dynamics and interaction properties.
    Journal of the Optical Society of America B 12/2014; 32(2). · 1.81 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Spin-orbit coupling (SOC) plays a crucial role in many branches of physics. In this context, the recent experimental realization of the coupling between spin and linear momentum of ultra-cold atoms opens a completely new avenue for exploring new spin-related superfluid physics. Here we propose that another important and fundamental SOC, the coupling between spin and orbital angular momentum (SOAM), can be implemented for ultra-cold atoms using higher order Laguerre-Gaussian laser beams to induce Raman coupling between two hyperfine spin states of atoms. We study the ground state phase diagrams of SOAM coupled Bose-Einstein condensates on a ring trap and explore their applications in gravitational force detection. Our results provide the basis for further investigation of intriguing superfluid physics induced by SOAM coupling.
    arXiv:1411.1737. 11/2014;


1 Download
Available from