Gap formation and soft phonon mode in the Holstein model

TL;DR

This paper explores how electron-phonon interactions lead to gap formation and soft phonon modes in the Holstein model, revealing precursor effects and Kondo-like physics through advanced theoretical methods.

Contribution

It introduces a non-perturbative approach combining dynamical mean-field theory and numerical renormalization group to study gap formation in the Holstein model.

Findings

Identification of precursor effects to gap formation

Observation of soft phonon modes and lattice fluctuations

Linking phonon behavior to Kondo-like physics

Abstract

We investigate electron-phonon coupling in many-electron systems using dynamical mean-field theory in combination with the numerical renormalization group. This non-perturbative method reveals significant precursor effects to the gap formation at intermediate coupling strengths. The emergence of a soft phonon mode and very strong lattice fluctuations can be understood in terms of Kondo-like physics due to the development of a double-well structure in the effective potential for the ions.