Superconducting dome in ferroelectric-type materials from soft mode instability

TL;DR

This paper proposes a minimal theoretical model explaining how soft mode instabilities in ferroelectric-like materials can enhance superconductivity, highlighting the role of anharmonic phonon damping modulated by external parameters.

Contribution

It introduces a simple theoretical framework linking soft mode dynamics and superconducting enhancement, emphasizing the impact of anharmonic phonon damping.

Findings

Superconducting critical temperature $T_c$ increases near the ferroelectric transition.

Soft mode damping plays a crucial role in superconductivity enhancement.

External control parameters modulate phonon damping and influence $T_c$.

Abstract

We present a minimal theory of superconductivity enhancement in ferroelectric-type materials. Simple expressions for the optical mode responsible for the soft mode transition are assumed. A key role is played by the anharmonic phonon damping which is modulated by an external control parameter (electron doping or mechanical strain) causing the appearance of the soft mode. It is shown that the enhancement in the superconducting critical temperature $T_{c}$ upon approaching the ferroelectric transition from either side is due to the Stokes electron-phonon scattering processes promoted by strong phonon damping effects.