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A new many-body wave function for BCS-BEC crossover in Fermi gases

Shina Tan·K. Levin
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Abstract

We present a new many body formalism for BCS-BEC crossover, which represents a modification of the BCS-Leggett ground state to include 4-fermion, and higher correlations. In the BEC regime, we show how our approach contains the \textit{Petrov et al} 4-fermion behavior and associated scattering length $a_{dd}$ at short distances, and secondly reduces to composite-boson Bogoliubov physics at long distances. It reproduces the Lee-Yang term, whose numerical value is also fixed by $a_{dd}$. We have also examined the next term beyond the Lee-Yang correction in a phenomenological fashion, building on cloud size data and collective mode experiments. However, one has to view this phenomenological analysis with some caution since experiments are in a state of flux and are performed close to unitarity.

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Shina Tan, K. Levin. 2006-10-15. A new many-body wave function for BCS-BEC crossover in Fermi gases. https://doi.org/10.1103/physreva.74.043606

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