Robustness of a local Fermi Liquid against Ferromagnetism and Phase Separation

TL;DR

This paper investigates the stability of local Fermi Liquids under various interactions, demonstrating suppression of ferromagnetism and phase separation, and analyzing their behavior near the metal-insulator transition with relevance to Sr_{1-x}La_xTiO_3.

Contribution

It provides a theoretical analysis of local Fermi Liquids showing constraints on instabilities and their behavior near the metal-insulator transition, supported by experimental consistency.

Findings

Ferromagnetism and phase separation are suppressed in local Fermi Liquids.

Superconductivity is limited to an s-wave channel.

The Wilson ratio approaches 2 near the metal-insulator transition.

Abstract

We study the properties of Fermi Liquids with the microscopic constraint of a local self-energy. In this case the forward scattering sum-rule imposes strong limitations on the Fermi-Liquid parameters, which rule out any Pomeranchek instabilities. For both attractive and repulsive interactions, ferromagnetism and phase separation are suppressed. Superconductivity is possible in an s-wave channel only. We also study the approach to the metal-insulator transition, and find a Wilson ratio approaching 2. This ratio and other properties of Sr_{1-x}La_xTiO_3 are all consistent with the local Fermi Liquid scenario.