Anomalous thermodynamic properties of quantum critical superconductors

TL;DR

This paper investigates how quantum critical magnetic fluctuations influence thermodynamic properties like heat capacity and penetration depth in superconductors, explaining observed anomalies near the quantum critical point.

Contribution

It demonstrates that quantum critical fluctuations can cause nodal-like behavior and renormalize penetration depth slopes in fully gapped superconductors, providing a new understanding of experimental anomalies.

Findings

Quantum critical fluctuations induce nodal-like temperature dependence.

Fluctuations cause significant renormalization of penetration depth slope.

Results are broadly applicable beyond the specific model used.

Abstract

Recent high-precision measurements employing different experimental techniques have unveiled an anomalous peak in the doping dependence of the London penetration depth which is accompanied by anomalies in the heat capacity in iron-pnictide superconductors at the optimal composition associated with the hidden antiferromagnetic quantum critical point. We argue that finite temperature effects can be a cause of observed features. Specifically we show that quantum critical magnetic fluctuations under superconducting dome can give rise to a nodal-like temperature dependence of both specific heat and magnetic penetration depth in a fully gapped superconductor. In the presence of line nodes in the superconducting gap fluctuations can lead to the significant renormalization of the relative slope of $T$-linear penetration depth which is steepest at the quantum critical point. The results we obtain are general and can be applied beyond the model we use.