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arXiv · 1203.3325

Atypical BCS-BEC crossover induced by quantum-size effects

A. A. Shanenko·M. D. Croitoru·A. V. Vagov·V. M. Axt·A. Perali·F. M. Peeters
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Abstract

Quantum-size oscillations of the basic physical characteristics of a confined fermionic condensate are a well-known phenomenon. Its conventional understanding is based on the single-particle physics, whereby the oscillations follow the size-dependent changes in the single-particle density of states. Here we present a study of a cigar-shaped ultracold superfluid Fermi gas, which demonstrates an important many-body aspect of the quantum-size effects, overlooked previously. The many-body physics is revealed in the atypical crossover from the Bardeen-Cooper-Schrieffer (BCS) superfluid to the Bose-Einstein condensate (BEC) induced by the size quantization of the particle motion. Quantized perpendicular spectrum results in the formation of single-particle subbands (shells) so that the aggregate fermionic condensate becomes a coherent mixture of subband condensates. Each time when the lower edge of a subband crosses the chemical potential, the BCS-BEC crossover is approached in this subband, and the aggregate condensate contains both the BCS and BEC-like components.

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A. A. Shanenko, M. D. Croitoru, A. V. Vagov, V. M. Axt, A. Perali, F. M. Peeters. 2012-09-14. Atypical BCS-BEC crossover induced by quantum-size effects. https://doi.org/10.1103/physreva.86.033612

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