Fluctuation-driven topological transition of binary condensates in optical lattices

Abstract

We examine the role of thermal fluctuations in two-species Bose-Einstein condensates confined in quasi-twodimensional (quasi-2D) optical lattices using the Hartree-Fock-Bogoliubov theory with the Popov approximation. The method, in particular, is ideal to probe the evolution of quasiparticle modes at finite temperatures. Our studies show that the quasiparticle spectrum in the phase-separated domain of the two-species Bose-Einstein condensate has a discontinuity at some critical value of the temperature. Furthermore, the low-lying modes like the slosh mode becomes degenerate at this critical temperature, and this is associated with the transition from the immiscible side-by-side density profile to the miscible phase. Hence, the rotational symmetry of the condensate density profiles are restored, and so is the degeneracy of quasiparticle modes.

Quantum-Granularity Effect in the Formation of Supermixed Solitons in Ring Lattices

“…The behaviour of the latter is ruled by the competition among tunnelling processes (resulting from the spatial fragmentation of the condensates into separated wells), intra-and the inter-species couplings. Such interplay among different contributions in the overall energy balance of the system results, among the rest, in a rich scenario of mixing-demixing quantum phase transitions [5,6,7,8,9], in the emergence of novel quantum phases [10,11,12], in the possibility of entangling [13,14] the two bosonic species, and in that of triggering peculiar dynamical regimes [15,16].…”

Collective modes in multicomponent condensates with anisotropy

“…For α < 0.8, both the branches continue to soften but at α ≈ 0.7 the branches start to harden. The hardening and softening of the low energy quasiparticle modes have also been observed around the point of phase separation of TBECs in optical lattices [31,32], and due to the change in the geometry and topology of the confining potential [4]. The dispersion curves are computed based on Eq.…”

Weakly-Interacting Bose–Bose Mixtures from the Functional Renormalisation Group

“…To continue we need an expression for both ∂ k W k and δ J φ. By differentiating Equation (18) with respect to k we obtain…”

“…Because of the bosonic nature of both species, Bose-Bose mixtures can show a plethora of rich phenomena non-present in their fermionic counterparts. On top of having two separate superfluids at low temperatures, Bose-Bose mixtures can show phase separation [17,18], droplet and liquid phases [19], spin drag [20,21], spin-orbit coupling [22], amongst other phenomena. Experimentally, Bose-Bose mixtures were rapidly achieved after the first BEC experiments, both using atoms in two different spin states [23][24][25] and of two different atom species [26].…”