Backflow in a Fermi Liquid

TL;DR

This paper calculates the backflow current around an impurity in a Fermi liquid, revealing a leading radial 1/r^2 contribution and a next-order dipolar 1/r^3 term, with implications for screening and friction.

Contribution

It provides an all-orders calculation of backflow contributions in a Fermi liquid, including a novel sum rule for phase shifts in the charged case.

Findings

Leading backflow contribution is radial and proportional to 1/r^2.

Dipolar 1/r^3 backflow is the next-to-leading term.

Friction force is determined solely by the leading backflow contribution.

Abstract

We calculate the backflow current around a fixed impurity in a Fermi liquid. The leading contribution at long distances is radial and proportional to 1/r^2. It is caused by the current induced density modulation first discussed by Landauer. The familiar 1/r^3 dipolar backflow obtained in linear response by Pines and Nozieres is only the next to leading term, whose strength is calculated here to all orders in the scattering. In the charged case the condition of perfect screening gives rise to a novel sum rule for the phase shifts. Similar to the behavior in a classical viscous liquid, the friction force is due only to the leading contribution in the backflow while the dipolar term does not contribute.