Atypical BCS-BEC crossover induced by quantum-size effects

• Published in: arXiv.org
• Main Authors: Shanenko, A A, Croitoru, M D, Vagov, A V, Axt, V M, Perali, A, Peeters, F M
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 14.09.2012
• Subjects: Chemical potential; Condensates; Crossovers; Fluids; Matter & antimatter; Organic chemistry; Oscillations; Particle density (concentration); Particle motion; Particle physics; Physical properties; Physics - Quantum Gases; Physics - Superconductivity; Size effects; Superfluidity
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1203.3325

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.