Comment on ``$T$-dependence of the magnetic penetration depth in unconventional superconductors at low temperatures: Can it be linear?"

TL;DR

This paper discusses the stability of d-wave superconductors at low temperatures, arguing that non-local effects prevent thermodynamic instability as temperature approaches zero.

Contribution

It clarifies that non-local effects inherently prevent the thermodynamic instability of d-wave superconductors at low temperatures.

Findings

Non-local effects prevent instability in d-wave superconductors at low T.

The stability issue raised by SD can be resolved by considering non-local effects.

The thermodynamic stability of unconventional superconductors is maintained at low temperatures.

Abstract

We comment on a recent letter by Schopohl and Dolgov (SD) which raised the possibility that a d-wave superconductor might be thermodynamically unstable in the limit $T\to 0$. The point of our comment is that this instability can be inevitably prevented by the non-local effects.