Strong Coupling Effects on the Specific Heat of an Ultracold Fermi Gas in the Unitarity Limit

Abstract

We investigate strong-coupling corrections to the specific heat $C_V$ in the normal state of an ultracold Fermi gas in the BCS-BEC crossover region. A recent experiment on a ${}^6$Li unitary Fermi gas [M. J. H. Ku, {\it et. al.}, Science {\bf 335}, 563 (2012)] shows that $C_V$ is remarkably amplified near the superfluid phase transition temperature $T_{\mathrm{c}}$, being similar to the well-known $\lambda$-structure observed in liquid ${}^4$He. Including pairing fluctuations within the framework of the strong-coupling theory developed by Nozières and Schmitt-Rink, we show that strong pairing fluctuations are sufficient to explain the anomalous behavior of $C_V$ observed in a ${}^6$Li unitary Fermi gas near $T_{\mathrm{c}}$. We also show that there is no contribution from {\it stable} preformed Cooper pairs to $C_V$ at the unitarity. This indicates that the origin of the observed anomaly is fundamentally different from the case of liquid ${}^4$He, where {\it stable} ${}^4$He Bose atoms induce the $\lambda$-structure in $C_V$ near the superfluid instability. Instead, the origin is the suppression of the entropy $S$, near $T_{\mathrm{c}}$, due to the increase of {\it metastable} preformed Cooper pairs. Our results indicate that the specific heat is a useful quantity to study the effects of pairing fluctuations on the thermodynamic properties of an ultracold Fermi gas in the BCS-BEC crossover region.

7 pages, 3 figures

References in corpus (8)

• Vortices and Superfluidity in a Strongly Interacting Fermi Gas
• Revealing the Superfluid Lambda Transition in the Universal Thermodynamics of a Unitary Fermi Gas
• Collective excitations of a degenerate gas at the BEC-BCS crossover
• Thermodynamics of the BCS-BEC crossover
• Thermodynamic Measurements in a Strongly Interacting Fermi Gas
• Evolution of the Normal State of a Strongly Interacting Fermi Gas from a Pseudogap Phase to a Molecular Bose Gas
• Comparative study of strong coupling theories of a trapped Fermi gas at unitarity
• Temperature of a trapped unitary Fermi gas at finite entropy

Cited by in corpus (1)

• Mechanisms of anomalous three-body loss in a population-imbalanced three-component Fermi gas