Relations involving the forward scattering amplitude in a Fermi gas

Shina Tan

Robert C. Forrey, A. Dalgarno, Jörg Schmiedmayer

We describe a method for measuring the forward-scattering amplitude for electron collisions with atoms or molecules. Our scheme uses a gas cell in one arm of an electron interferometer and measures the resulting attenuation and phase shift of the electron matter wave. The complex index of refraction of the gas is determined along with the forward-scattering amplitude. Calculations of the scattering of electrons by atoms are performed using a self-energy potential obtained by treating the atom as an inhomogeneous electron gas. The results indicate that the proposed experiments are feasible.

Е. А. Иванченко, V. D. Tsukanov

J. J. Kinnunen

The Hartree energy shift is calculated for a unitary Fermi gas. By including the momentum dependence of the scattering amplitude explicitly, the Hartree energy shift remains finite even at unitarity. Extending the theory also for spin-imbalanced systems allows calculation of polaron properties. The results are in good agreement with more involved theories and experiments.

M. A. Baranov, M. Yu. Kagan

A general model-independent justification is given for the assertion that a superconducting transition is possible in a Fermi gas with repulsion. It is shown for a wide class of systems that at least one harmonic of the effective interaction is attractive. A relation is found between the harmonics of the effective interaction and the harmonics of the quasiparticle scattering amplitude in the gas approximation.

S. Laalitya Uppalapati, Daniel E. Sheehy