We theoretically investigate the specific heat
CV 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
CV as a function of temperature varies, as one moves from the weak-coupling regime to the strong-coupling limit. In the weak-coupling regime,
CV is shown to be enhanced by
p-wave pairing fluctuations, near the superfluid phase transition temperature
Tc. Similar enhancement of
CV(T≃Tc) 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
Tc.
We investigate the specific heat
CV at constant volume and effects of uniaxial anisotropy of a
p-wave attractive interaction in the normal state of an ultracold Fermi gas. Within the framework of the strong-coupling theory developed by Nozières and Schmitt-Rink, we evaluate this thermodynamic quantity as a function of temperature, in the whole interaction regime. While the uniaxial anisotropy is not crucial for
CV in the weak-coupling regime,
CV is found to be sensitive to the uniaxial anisotropy in the strong-coupling regime. This originates from the population imbalance among
pi-wave molecules (
i=x,y,z), indicating that the specific heat is a useful observable to see which kinds of
p-wave molecules dominantly exist in the strong-coupling regime when the
p-wave interaction has uniaxial anisotropy. Using this strong point, we classify the strong-coupling regime into some characteristic regions. Since a
p-wave pairing interaction with uniaxial anisotropy has been discovered in a
40K Fermi gas, our results would be useful in considering strong-coupling properties of a
p-wave interacting Fermi gas, when the interaction is uniaxially anisotropic.
We investigate the superfluid properties of a one-component Fermi gas with a uniaxially anisotropic
p-wave pairing interaction,
Ux>Uy=Uz [where
Ui(i=x,y,z) is a
pi-wave pairing interaction]. This type of interaction is considered to be realized in a
40K Fermi gas. Including pairing fluctuations within a strong-coupling
T-matrix theory, we determine the
px-wave superfluid phase transition temperature
Tcpx, as well as the other phase transition temperature
Tcpx+ipy(<Tcpx), below which the superfluid order parameter has the
px+ipy-wave symmetry. In the normal state near
Tcpx,px-wave pairing fluctuations are shown to induce an anisotropic pseudogap phenomenon, where a dip structure in the angle-resolved density of states around $\ensuremath{\omega}=0$ is the most remarkable in the
px direction. In the
px-wave superfluid phase $({T}_{\mathrm{c}}^{{p}_{x}+i{p}_{y}}<T\ensuremath{\le}{T}_{\mathrm{c}}^{{p}_{x}})$, while the pseudogap in the
px direction continuously changes to the superfluid gap, the pseudogap in the perpendicular direction to the
px axis is found to continue developing because of enhanced
py-wave and
pz-wave pairing fluctuations around the node of the
px-wave superfluid order parameter. Since pairing fluctuations are always suppressed in the isotropic
s-wave superfluid state, this phenomenon is peculiar to an unconventional Fermi superfluid with a nodal superfluid order parameter. Since the
p-wave Fermi superfluid is the most promising non-
s-wave pairing state in an ultracold Fermi gas, our results would contribute to understanding how the anisotropic pairing fluctuations, as well as the existence of plural superfluid phases, affect many-body properties of this unconventional Fermi superfluid.
We investigate single-particle properties of a one-component Fermi gas with a tunable
p-wave interaction. Including pairing fluctuations associated with this anisotropic interaction within a
T-matrix theory, we calculate the single-particle density of states, as well as the spectral weight, above the superfluid transition temperature
Tc. Starting from the weak-coupling regime, we show that the so-called pseudogap first develops in these quantities with increasing the interaction strength. However, when the interaction becomes strong to some extent, the pseudogap becomes obscure to eventually disappear in the intermediate coupling regime. In the strong-coupling regime, the excitation gap associated with the formation of tightly bound molecules again opens. This nonmonotonic interaction dependence of the excitation gap is quite different from the case of an
s-wave interaction, where the pseudogap simply develops with increasing the interaction strength, which continuously changes into the molecular excitation gap. The difference between the two cases is shown to originate from the momentum dependence of the
p-wave interaction, which vanishes in the low momentum limit. We also identify the pseudogap regime in the phase diagram with respect to the temperature and the
p-wave interaction strength. Since the pseudogap is a precursor phenomenon of the superfluid phase transition, our results would be useful for the research toward the realization of
p-wave superfluid Fermi gases.
We investigate fluctuation effects in a single-component ultracold Fermi gas with a p-wave interaction. Within the framework of a strong-coupling T-matrix theory, we calculate the single-particle density of states (DOS) at the superfluid phase transition temperature Tc. Starting from the weak-coupling regime, we show that the so-called pseudogap structure develops in DOS, with increasing the strength of a pairing interaction. However, in contrast to the case of s-wave interaction (where the pseudogap size in DOS monotonically increases with increasing the interaction strength), the pseudogap structure is found to gradually disappear in the strong-coupling regime. We point out that this non-monotonic behavior of pseudogap originates from the momentum dependence of p-wave interaction. Our results clarify how the symmetry of pairing interaction affects pseudogap phenomena in strongly correlated fermion systems.
We theoretically investigate the specific heat at constant volume C V in the BCS(Bardeen-Cooper-Schrieffer)-BEC(Bose-Einstein-condensation)-crossover regime of an ultracold Fermi gas, below the superfluid phase transition temperature T c . Within the strong-coupling framework developed by Nozières and Schmitt-Rink, we show that the temperature dependence of C V drastically changes as one passes through the crossover region, and is sensitive to strong fluctuations in the Cooper channel near the unitarity limit. We also compare our results to a recent experiment on a 6 Li unitary Fermi gas. Since fluctuation effects are a crucial key in the BCS-BEC-crossover phenomenon, our results would be helpful in considering how the fermionic BCS superfluid changes into BEC with increasing the interaction strength, from the viewpoint of specific heat.