Understanding the formation of Cooper pairs and the resulting thermodynamic properties of low-dimensional Fermi gases is an important area of research, which may help build our understanding of other low-dimensional systems, such as high-temperature superconductors. In lower dimensions, quantum fluctuations are expected to play an increasingly important role, and the reliability of strong-coupling theories becomes questionable. Here, we present a comparison of recent thermodynamic measurements and theoretical predictions from different many-body $T$ -matrix theories for a two-dimensional strongly interacting Fermi gas in the normal state. We find that the fully self-consistent $T$ -matrix theory provides the best description of the experimental data over a wide range of temperatures and interatomic interactions.Understanding the formation of Cooper pairs and the resulting thermodynamic properties of low-dimensional Fermi gases is an important area of research, which may help build our understanding of other low-dimensional systems, such as high-temperature superconductors. In lower dimensions, quantum fluctuations are expected to play an increasingly important role, and the reliability of strong-coupling theories becomes questionable. Here, we present a comparison of recent thermodynamic measurements and theoretical predictions from different many-body $T$-matrix theories for a two-dimensional strongly interacting Fermi gas in the normal state. We find that the fully self-consistent $T$-matrix theory provides the best description of the experimental data over a wide range of temperatures and interatomic interactions.

arXiv:1509.08225Physical Review ADec 29, 201526 citations

Pseudogap regime of a strongly interacting two-dimensional Fermi gas with and without confinement-induced effective range of interactions

Brendan C. Mulkerin, Xia-Ji Liu, Hui Hu

We investigate theoretically the many-body pairing of a strongly correlated two-dimensional Fermi gas with and without negative confinement-induced effective range. Using a strong-coupling effective field theory in the normal state, we show that the specific heat at constant volume can be used as a characteristic indicator of the crossover from the normal Fermi liquid to the pseudogap state in two dimensions. We calculate the pseudogap formation temperature through the specific heat at constant volume, examining the role of a negative confinement-induced effective range on many-body pairing above the superfluid transition. We compare our results with and without effective range to the recent experimental measurement performed with radio-frequency spectroscopy in Murthy et al. [P. A. Murthy, M. Neidig, R. Klemt, L. Bayha, I. Boettcher, T. Enss, M. Holten, G. Z\"urn, P. M. Preiss, and S. Jochim, Science 359, 452 (2018)]. Although a good qualitative agreement is found, we are not able to discriminate the effect of the confinement-induced effect range in the experimental data.We investigate theoretically the many-body pairing of a strongly correlated two-dimensional Fermi gas with and without negative confinement-induced effective range. Using a strong-coupling effective field theory in the normal state, we show that the specific heat at constant volume can be used as a characteristic indicator of the crossover from the normal Fermi liquid to the pseudogap state in two dimensions. We calculate the pseudogap formation temperature through the specific heat at constant volume, examining the role of a negative confinement-induced effective range on many-body pairing above the superfluid transition. We compare our results with and without effective range to the recent experimental measurement performed with radio-frequency spectroscopy in Murthy et al. [P. A. Murthy, M. Neidig, R. Klemt, L. Bayha, I. Boettcher, T. Enss, M. Holten, G. Z\"urn, P. M. Preiss, and S. Jochim, Science 359, 452 (2018)]. Although a good qualitative agreement is found, we are not able to discriminate the effect of the confinement-induced effect range in the experimental data.

arXiv:2003.06095Physical Review AJul 15, 20209 citations

Strong-Coupling Properties of ap-Wave Interacting Fermi Gas on the Viewpoint of Specific Heat at Constant Volume

Daisuke Inotani, Pieter van Wyk, Yoji Ohashi

We theoretically investigate the specific heat $C_V$ at constant volume in the normal state of a $p$ -wave interacting Fermi gas. Including fluctuations in the $p$ -wave Cooper channel within the framework of the strong-coupling theory developed by Nozières and Schmitt-Rink, we clarify how $C_V$ as a function of temperature varies, as one moves from the weak-coupling regime to the strong-coupling limit. In the weak-coupling regime, $C_V$ is shown to be enhanced by $p$ -wave pairing fluctuations, near the superfluid phase transition temperature $T_{\rm c}$ . Similar enhancement of $C_V(T\simeq T_{\rm c})$ is also obtained in the strong-coupling regime, which, however, reflects that system is close an ideal Bose gas of $p$ -wave two-body bound molecules. Using these results, we classify the normal state into (1) the normal Fermi gas regime, (2) the $p$ -wave molecular Bose gas regime, and (3) the region between the two, where $p$ -wave pairing fluctuations are dominant. Since the current experiments can only access the normal phase of a $p$ -wave interacting Fermi gas, our results would be useful for experiments to understand strong-coupling properties of this Fermi system above $T_{\rm c}$ .We theoretically investigate the specific heat $C_V$ at constant volume in the normal state of a $p$-wave interacting Fermi gas. Including fluctuations in the $p$-wave Cooper channel within the framework of the strong-coupling theory developed by Nozières and Schmitt-Rink, we clarify how $C_V$ as a function of temperature varies, as one moves from the weak-coupling regime to the strong-coupling limit. In the weak-coupling regime, $C_V$ is shown to be enhanced by $p$-wave pairing fluctuations, near the superfluid phase transition temperature $T_{\rm c}$. Similar enhancement of $C_V(T\simeq T_{\rm c})$ is also obtained in the strong-coupling regime, which, however, reflects that system is close an ideal Bose gas of $p$-wave two-body bound molecules. Using these results, we classify the normal state into (1) the normal Fermi gas regime, (2) the $p$-wave molecular Bose gas regime, and (3) the region between the two, where $p$-wave pairing fluctuations are dominant. Since the current experiments can only access the normal phase of a $p$-wave interacting Fermi gas, our results would be useful for experiments to understand strong-coupling properties of this Fermi system above $T_{\rm c}$.

arXiv:1610.08598Journal of the Physical Society of JapanJan 26, 20173 citations

The Equation of State of a Strongly Interacting Fermi Gas

Nir Navon, Sylvain Nascimb `ene, Kaijun Jiang +2 more

Bulletin of the American Physical SocietyMay 29, 20100 citations

T

-matrix theories for a two-dimensional strongly interacting Fermi gas in the normal state. We find that the fully self-consistent

T

-matrix theory provides the best description of the experimental data over a wide range of temperatures and interatomic interactions.

We theoretically investigate the specific heat

C_V

at constant volume in the normal state of a

p

-wave interacting Fermi gas. Including fluctuations in the

p

-wave Cooper channel within the framework of the strong-coupling theory developed by Nozières and Schmitt-Rink, we clarify how

C_V

as a function of temperature varies, as one moves from the weak-coupling regime to the strong-coupling limit. In the weak-coupling regime,

C_V

is shown to be enhanced by

p

-wave pairing fluctuations, near the superfluid phase transition temperature

T_{\rm c}

. Similar enhancement of

C_V(T\simeq T_{\rm c})

is also obtained in the strong-coupling regime, which, however, reflects that system is close an ideal Bose gas of

p

-wave two-body bound molecules. Using these results, we classify the normal state into (1) the normal Fermi gas regime, (2) the

p

-wave molecular Bose gas regime, and (3) the region between the two, where

p

-wave pairing fluctuations are dominant. Since the current experiments can only access the normal phase of a

p

-wave interacting Fermi gas, our results would be useful for experiments to understand strong-coupling properties of this Fermi system above

T_{\rm c}