We make use of Shannon entropy (
S) and Fisher information (
I) to study the response of atomic density profiles of a spin-orbit coupled Bose-Einstein condensate to changes in the wave number (
κL) of the Raman laser that couples two hyperfine states of atoms in the condensate. The choice for values of
κL, the so-called spin-orbit parameter, and Rabi frequency (
Ω) leads to two distinct regions in the system's energy spectrum with different order parameters and/or probability densities. In addition, we can have a spatially modulated density profile, reminiscent of the so called stripe phase. Our numbers for
S and
I demonstrate that for
κL2Ω (region 2) for increasing values of
κL. In the stripe phase the nature of
S and
I to changes in
κL is similar to that found for the condensate in region 2. The results for information theoretic quantities in the stripe phase are, in general, augmented compared to those of region 2. In particular, the highly enhanced values of position-space Fisher information imply an extremely concentrated atomic density distribution to provide an evidence for supersolid properties of Bose-Einstein condensates in the presence of spin-orbit coupling.
Abstract We consider an attractive quasi-one dimensional spin-orbit coupled Bose–Einstein condensate (SOC BEC) confined in a periodic potential produced by the combination of linear and nonlinear optical lattices, and study the effects of squeezing a stripe soliton by varying the inter-atomic interaction in the nonlinear lattice. It is observed that the nodes on the soliton arising entirely due to the effect of spin–orbit coupling tend to disappear as we increase the squeezing effect to finally get a stable fundamental soliton. This leads us to conclude that external pressure can reduce the effect of spin–orbit coupling in the SOC BEC and even convert the system to a traditional BEC without spin–orbit coupling. We make use of an information theoretic measure to visualize how does the atomic density distribution in the condensate respond to continual reduction in the spin–orbit coupling effect.
In this paper, we consider the ground state properties of a spin-orbit coupled binary Bose-Einstein condensates with dipole-dipole interaction.Our results are obtained by numerically solving the Gross-Pitaevskii equation in the mean field.It is shown that the density structures are greatly affected by spin-orbit coupled strength and dipole strength.With the increase of spin-orbit coupled strength, we find that a stripe phase and phase separation of two components appear, and the number of stripes increases.In addition, concentric circularity stripes with spatial symmetry appear.We also verify that the phase separation can be broken as the dipole strength increases.However, the stripe phase is still kept in this process.As a result, there are no regions of zero density inside the cloud and the nonfragmented density BEC is exhibited.Also, the critical dipole strength decreases with increasing the SOC strength for the non-fragmented state.This result reflects a competition in which the spin-orbit coupling dominates the dipole-dipole interaction.
Supersolidity---a coexistence of superfluidity and crystalline or amorphous density variations---has been vividly debated ever since its conjecture. While the initial focus was on helium-4, recent experiments uncovered supersolidity in ultracold dipolar quantum gases. Here we propose a self-bound supersolid phase in a binary mixture of Bose gases with short-range interactions, making use of the nontrivial properties of spin-orbit coupling. We find that a first-order phase transition from a self-bound supersolid stripe phase to a zero-minimum droplet state of the Bose gas occurs as a function of the Rabi coupling strength. These phases are characterized using the momentum distribution, the transverse spin polarization, and the superfluid fraction. The critical point of the transition is estimated in an analytical framework. The predicted density-modulated supersolid stripe and zero-minimum droplet phase should be experimentally observable in a binary mixture of
39K with spin-orbit coupling.
We study the collective dynamics of the spin-orbit coupled two pseudospin components of a Bose-Einstein condensate trapped in a quasi-one-dimensional harmonic potential, by using variational and directly numerical approach of binary mean-field Gross-Pitaevskii equations. The results show that, because of strong coupling of spin-orbit coupling (SOC), Rabi coupling, and atomic interaction, the collective dynamics of the system behave as complex characters. When the Rabi coupling is absent, the density profiles of the system preserve the Gauss type and the wave packets do harmonic oscillations. The amplitude of the collective oscillations increases with SOC. Furthermore, when the SOC strength increases, the dipole oscillations of the two pseudospin components undergo a transition from in-phase to out-of-phase oscillations. When the Rabi coupling present, there will exist a critical value of SOC strength (which depends on the Rabi coupling and atomic interaction). If the SOC strength is less than this critical value, the density profiles of the system can preserve the Gauss type and the wave packets do anharmonic (the frequency of dipole oscillations depends on SOC) oscillations synchronously (i.e., in-phase oscillations). However, if the SOC strength is larger than this critical value, the wave packets are dynamically fragmented and the stable dipole oscillations of the system can not exist. The collective dynamics of the system can be controlled by adjusting the atomic interaction, SOC, and Rabi-coupling strength.
The phases of a Bose-Einstein condensate (BEC) with light-induced spin-orbit coupling (SOC) are studied within the mean-field approximation. The mixed BEC phase, in which the system condenses in a superposition of two plane-wave states, is found to be stable for sufficiently small light-atom coupling, becoming unstable in a continuous fashion with increasing light-atom coupling. The structure of the phase diagram at fixed chemical potential for bosons with SOC is shown to imply an unusual density dependence for a trapped mixed BEC phase, the density of one dressed spin state increasing with increasing radius, providing a unique experimental signature of this state. The collective Bogoliubov sound mode is shown to also provide a signature of the mixed BEC state, vanishing as the boundary to the regime of phase separation is approached.