Charge gap, lattice distortion, and ferroelastic fluctuations in high-temperature superconductors

TL;DR

This paper explores the connection between ferroelastic lattice distortions, charge ordering, and superconducting transition temperatures in high-temperature superconductors, highlighting the role of lattice fluctuations and charge gaps.

Contribution

It demonstrates that ferroelastic distortions are linked to superconductivity and introduces a relation between charge gaps and transition temperatures in layered tetragonal superconductors.

Findings

Ferroelastic lattice distortions are associated with superconducting transitions.

Charge ordering causes improper ferroelastic distortions in high-Tc superconductors.

Ferroelastic fluctuations produce the specific heat jump at Tc.

Abstract

It is shown that a ferroelastic lattice distortion is associated with the superconducting transition both in low- and high-temperature superconductors. In layered tetragonal superconductors with a sufficiently high transition temperature, a ferroelastic distortion is improper and is caused by an out-of-plane charge ordering. The relation between the out-of-plane charge gap and the maximum superconducting transition temperature for these superconductors is obtained. It is shown also that the specific heat jump at the superconducting transition temperature in pnictide and cuprate superconductors is produced by ferroelastic fluctuations just below the transition temperature. The amplitude of the corresponding lattice distortion is estimated.