Theoretical approaches to the momentum distribution of a normal Fermi liquid

Mohammed Serhan, MANFRED L. RISTIG

Zsolt Gulácsi, Iván Orlik

We are reporting a new non-Fermi-liquid-type normal phase that has a well defined Fermi energy, but without showing any non-regularity in the momentum distribution function n k in the whole momentum space, the sharp Fermi momentum concept being undefinable. The system contains a natural built-in gap that is visible in the physical properties of the system at nonzero temperatures. The presence of a flat band in multi-band interacting Fermi systems with more than half filling is the key feature leading to such a ground state, which is not restricted to one spatial dimension and emerges in the proximity of an insulating phase.

M. F. Flynn

Imran Siddique

A. N. Tarasov

General expressions are obtained in explicit form for the anomalous and normal distribution functions of quasiparticles in nonunitary phases of a superfluid paramagnetic Fermi liquid consisting of electrically neutral fermions with triplet pairing (the pairs have spin s=1 and an arbitrary odd value of the orbital angular momentum l) in a uniform static magnetic field. A generalized Fermi-liquid approach is used which takes into account the exchange Fermi-liquid interaction but does not specify the form of the energy functional of the superfluid Fermi liquid. The results are valid at any temperature in the interval 0⩽T⩽Tc, where Tc is the temperature of the phase transition from the normal to the superfluid state. When an explicit form of the energy functional is specified, the general formulas for the distribution function can be used to describe the various nonunitary phases of a superfluid Fermi liquid of the He3 type in a high magnetic field. In particular, for He3-A1, He3-A2, and the nonunitary two-dimensional phase of He3 in a high magnetic field at 0⩽T⩽Tc, an energy functional quadratic in the distribution function is used to find a system of coupled equations for the order parameter and the effective magnetic field and to obtain an expression is obtained for the nonlinear magnetic susceptibility.

Xiao-Xia Ruan, Hao Ran Gong, Zhengling Wang +1 more

We compute the momentum distribution of a homogeneous Fermi gas at unitarity in the normal phase within the framework of the non-self-consistent T-matrix approximation with particle-hole fluctuation. From the large-momentum behavior of momentum distribution, we obtain the contact for the unitary Fermi gas. We also compare our results with experimental data and other theoretical predictions.