Pauli susceptibility of nonadiabatic Fermi liquids

TL;DR

This paper investigates how nonadiabatic electron-phonon interactions alter the Pauli susceptibility in Fermi liquids, revealing reduced susceptibility and isotope dependence, contrasting with traditional adiabatic theories.

Contribution

It demonstrates that nonadiabatic effects decrease Pauli susceptibility and introduce isotope dependence, providing new insights into electron-phonon interactions beyond Migdal-Eliashberg theory.

Findings

Nonadiabatic corrections lower Pauli susceptibility.

Susceptibility exhibits isotope dependence in the nonadiabatic regime.

Contrasts with predictions from adiabatic Migdal-Eliashberg theory.

Abstract

The nonadiabatic regime of the electron-phonon interaction leads to behaviors of some physical measurable quantities qualitatively different from those expected from the Migdal-Eliashberg theory. Here we identify in the Pauli paramagnetic susceptibility $\chi$ one of such quantities and show that the nonadiabatic corrections reduce $\chi$ with respect to its adiabatic limit. We show also that the nonadiabatic regime induces an isotope dependence of $\chi$, which in principle could be measured.