Competing interactions in population-imbalanced two-component Bose-Einstein condensates

Abstract

We consider a two-component Bose-Einstein condensate with and without synthetic "spin-orbit" interactions in two dimensions. Density-and phase-fluctuations of the condensate are included, allowing us to study the impact of thermal fluctuations and density-density interactions on the physics originating with spin-orbit interactions. In the absence of spin-orbit interactions, we find that inter-component density interactions deplete the minority condensate. The thermally driven phase transition is driven by coupled density and phase-fluctuations, but is nevertheless shown to be a phase-transition in the Kosterlitz-Thouless universality class with close to universal amplitude ratios irrespective of whether both the minority-and majority condensates exist in the ground state, or only one condensate exists. In the presence of spin-orbit interactions we observe three separate phases, depending on the strength of the spin-orbit coupling and inter-component density-density interactions: a phasemodulated phase with uniform amplitudes for small intercomponent interactions, a completely imbalanced, effectively single-component, condensate for intermediate spin-orbit coupling strength and suficciently large inter-component interactions, and a phase-modulated and amplitude-modulated phase for sufficiently large values of both the spin-orbit coupling and the inter-component density-density interactions. The phase which is modulated by a single q-vector only is observed to transition into an isoptropic liquid through a strong depinning transition with periodic boundary conditions, which weakens with open boundaries. arXiv:1608.03300v1 [cond-mat.quant-gas]

Renormalization group flows of the N -component Abelian Higgs model

“…This result was also confirmed by separate Monte Carlo simulations [5][6][7], and the transition was conjectured to belong to the XY universality class [8,9]. The two component case was also studied in [10,11], and the question of the order of the transition in Ginzburg-Landau-type models has also drawn attention in systems with various symmetries and interactions [12][13][14].…”

“…where Γ k obeys the flow equation (8). Applying the substitutions ( 16) and ( 17) on the Ward-Takahashi identity (14), one arrives at the modified Ward-Takahashi identity:…”

Quantum dynamics of impurities in a Bose-Einstein condensate

“…Impurities dynamics in a Bose-Einstein condensate (BEC) offer an appealing platform to investigate profoundly imbalanced multicomponent systems [1][2][3][4]. Ultracold atoms provide one to manipulate and examine systems with population imbalance [5][6][7], and analogous impurity-impurity induced interactions [8][9][10][11]. The impurity interaction with the ultracold atoms offers the possibility for novel applications.…”