Abstract
We propose that novel superfluid with supersolid-like properties - angular stripe phase - can be realized in a pancake-like spin-1/2 Bose gas with spin-orbital-angular-momentum coupling. We predict a rich ground-state phase diagram, including the vortex-antivortex pair phase, half-skyrmion phase, and two different angular stripe phases. The stripe phases feature modulated angular density-density correlation with sizable contrast and can occupy a relatively large parameter space. The low-lying collective excitations, such as the dipole and breathing modes, show distinct behaviors in different phases. The existence of the novel stripe phase is also clearly indicated in the energetic and dynamic instabilities of collective modes near phase transitions. Our predictions of the angular stripe phase could be readily examined in current cold-atom experiments with $^{87}$Rb and $^{41}$K.
Highlights
Owing to the high controllability of degrees of freedom, ultracold atomic gases have became a versatile platform to study artificial gauge fields over the past few years [1,2]
We propose that a superfluid with supersolidlike properties, i.e., angular stripe phase, can be realized in a pancakelike spin-1/2 Bose gas with spin-orbital-angular-momentum coupling
The stripe phase is energetically favored for an intraspecies interaction strength larger than the interspecies one (e.g., g > g↑↓), and in a 87Rb gas with Raman spin-orbit coupling (SOC), it lies in a narrow window of Rabi frequency due to the small difference between g and g↑↓ [8]
Summary
Owing to the high controllability of degrees of freedom, ultracold atomic gases have became a versatile platform to study artificial gauge fields over the past few years [1,2]. The resulting SOAMC is of a two-dimensional (2D) nature with an axial symmetry, which gives rise to intriguing quantum phases, such as the vortex-antivortex pair phase (see phase I in Fig. 1) with definite angular momentum lz = 0, the half-skyrmion phase II with lz = hor −h, and the superposition phase III with an equal-weight combination of two angular-momentum states at lz = ±h [15,16] These are precisely the analogs of the zero-momentum, planewave, and stripe phases in the case of Raman SOC. In this paper we investigate ground-state phases and lowlying collective modes of a harmonically trapped pancakelike SOAMC Bose gas for realistic parameters using 87Rb and 41K atoms, by developing a self-consistent Gross-Pitaevskii theory within the Bogoliubov approximation and a variational theory at zero temperature The former theory concentrates on the case with definite angular momentum
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