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arXiv 2403.08482cond-mat.quant-gascond-mat.stat-mech
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总动量固定的正则系综中的玻色-爱因斯坦凝聚

Bose-Einstein condensation in canonical ensemble with fixed total momentum

Andrey S. Plyashechnik, Alexey A. Sokolik, Yurii E. Lozovik

AI总结:

该研究针对总动量与粒子数均固定的无相互作用三维玻色气体,通过鞍点法推导大N极限下的解析近似,预测了凝聚体碎裂现象,揭示了伽利略不变性破缺,拓展了运动量子系统的有限温度理论。

摘要:

我们研究了粒子数$N$和所有粒子的总动量$\textbf{P}$均固定时,无相互作用均匀三维气体在正则系综中的玻色-爱因斯坦凝聚。利用鞍点法,我们推导了配分函数、自由能以及不同单粒子能级占据数统计分布的大$N$解析近似。在相变临界点以下的温度中,我们预测在$\textbf{P}$的某些范围内会出现凝聚体碎裂,即不止一个单粒子能级被宏观占据。承载凝聚体的能级的占据数分布近似为高斯型,其他非凝聚体能级的占据数分布为指数型。我们的分析表明,在存在玻色-爱因斯坦凝聚的情况下,运动的有限温度多粒子系统的伽利略不变性被打破,并将运动和旋转量子系统的理论推广到了有限温度的大$N$极限。

英文摘要:

We consider Bose-Einstein condensation of noninteracting homogeneous three-dimensional gas in canonical ensemble when both particle number $N$ and total momentum $\mathbf{P}$ of all particles are fixed. Using the saddle point method, we derive the large-$N$ analytical approximations for partition function, free energy, and statistical distributions of occupation numbers of different single-particle energy levels. At temperatures below the critical point of phase transition, we predict, in some ranges of $\mathbf{P}$, fragmentation of the condensate, when more than one single-particle level is macroscopically occupied. The occupation number distributions have approximately Gaussian shapes for the levels hosting the condensate, and exponential shapes for other, noncondensate levels. Our analysis demonstrates breaking of Galilean invariance of moving finite-temperature many-particle system in the presence of Bose-Einstein condensation and extends the theory of moving and rotating quantum systems to the finite-temperature large-$N$ limit.

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