We study Bose-Einstein condensation (BEC) in three-dimensional two-component bosonic gases, characterizing the universal behaviors of the critical modes arising at the BEC transitions. For this purpose, we use field-theoretical (FT) renormalization-group (RG) methods and perform mean-field and numerical calculations. The FT RG analysis is based on the Landau-Ginzburg-Wilson Φ4 theory with two complex scalar fields which has the same symmetry as the bosonic system. In particular, for identical bosons with exchange Z2 symmetry, coupled by effective density-density interactions, the global symmetry is Z2,eàŠ - U(1)àŠ - U(1). At the BEC transition, it may break into Z2,eàŠ - Z2àŠ - Z2 when both components condense simultaneously, or to U(1)àŠ - Z2 when only one component condenses. This implies different universality classes for the corresponding critical behaviors. Numerical simulations of the two-component Bose-Hubbard model in the hard-core limit support the RG prediction: when both components condense simultaneously, the critical behavior is controlled by a decoupled XY fixed point, with unusual slowly decaying scaling corrections arising from the onsite interspecies interaction.
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机译:我们研究了二维两组分玻色气体中的玻色-爱因斯坦凝聚(BEC),表征了在BEC跃迁中产生的临界模式的普遍行为。为此,我们使用场理论(FT)重归一化组(RG)方法并执行均值场和数值计算。 FT RG分析基于Landau-Ginzburg-WilsonΦ4理论,具有两个复杂的标量场,其对称性与玻声子系统相同。特别是,对于具有交换Z2对称性且通过有效的密度-密度相互作用耦合的相同玻色子,全局对称性为Z2,eàŠ-U(1)à-U(1)。在BEC过渡时,当两个组件同时冷凝时,它可能会分解为Z2,e-Z2à-Z2,或者当只有一个组件冷凝时,它会分解为U(1)à-Z2。这意味着相应的关键行为具有不同的通用性类别。硬核极限中两组分Bose-Hubbard模型的数值模拟支持RG预测:当两个组分同时凝结时,临界行为由解耦的XY定点控制,并且在现场产生异常缓慢衰减的比例校正种间相互作用。
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