An unusual superconducting Isotope Effect in the presence of a Quantum Criticality

TL;DR

This paper explores how quantum critical points influence the isotope effect in superconductors, proposing a new experimental signature linking quantum criticality and superconductivity, especially near structural instabilities.

Contribution

It introduces a theoretical framework connecting isotope effects to quantum criticality, providing a way to identify QCPs through isotope exponent measurements in superconductors.

Findings

Derived the isotope exponent in terms of microscopic parameters.

Identified a distinct isotope effect signature near QCPs.

Linked structural instabilities to superconducting pairing mechanisms.

Abstract

We discuss the possible connection between superconductivity (SC) and quantum critical points (QCP) for any QCP that is tunable by isotopic mass substitution. We find a distinct contribution to the isotope exponent, due to the proximity to a QCP, which can be used as an experimental signature for the relation between SC and QCP. The relation is demonstrated in a scenario where the SC pairing is due to modes related to a structural instability. Within this model the isotope exponent is derived in terms of microscopic parameters.