Transition to miscibility in a binary Bose–Einstein condensate induced by linear coupling

Abstract

A one-dimensional mean-field model of a two-component condensate in the parabolic trap is considered, with the components corresponding to different spin states of the same atom. We demonstrate that the linear coupling (interconversion) between them, induced by a resonant electromagnetic wave, can drive the immiscible binary condensate into a miscible state. This transition is predicted in an analytical form by means of a variational approximation (for an infinitely long system), and is confirmed by direct numerical solutions of the symmetric and asymmetric models (the asymmetry accounts for a possible difference in the chemical potential between the components). We define an order parameter of the system as an off-centre shift of the centre of mass of each component. A numerically found dependence of the order parameter on the linear-coupling strength reveals a second-kind phase transition (in an effectively finite system). The phase transition looks very similar in two different regimes, namely, with a fixed number of atoms, or a fixed chemical potential. An additional transition is possible between double- and single-humped density distributions in the weak component of a strongly asymmetric system. We also briefly consider dynamical states, with the two components oscillating relative to each other. In this case, the components periodically separate even if they should be mixed in the static configuration.

Effects of axial vorticity in elongated mixtures of Bose-Einstein condensates

“…This is clearly a finite-size effect, since expression (12) vanishes at R → ∞. If the density is small enough, relations (9) and (10) may be approximated by σ 1 ≈ 1 and σ 2 ≈ 1/(m 1/4 Ω 1/2 ), and Eq.…”

“…The pressure induced by the transverse confinement changes the situation, pushing the system towards stronger miscibility (see, e.g., Ref. [12]). …”

Rabi Flopping Induces Spatial Demixing Dynamics

“…An alternative approach for the control of interaction properties and the corresponding dynamics in one-dimensional systems has been demonstrated using state-selective transversal confinement [11]. Recently it has been shown, that the miscibility characteristics of spinor gases can be changed using Raman coupling [12].In the present letter, we experimentally investigate the theoretically predicted miscibility properties of two spin states in a Bose-Einstein condensate in the presence of linear coupling [13][14][15]. We report on the experimental observation of the demixing dynamics of the relevant spin states, i.e.…”

Suppression of the quantum collapse in binary bosonic gases

“…This, in turn, allows one to switch the binary system between regimes of miscibility at γ < 1 and immiscibility at γ > 1 [17,18]. The point of the miscibility-immiscibility transition may be shifted from γ = 1 to γ > 1 by external confinement [19,20], and by linear mixing between the species [19,21], including the mixing which represents the effective spin-orbit coupling in binary condensates [22]. The immiscibility leads to the phase separation of binary condensates and formation of domain walls in the 1D geometry [23].…”