Comment on "Is the nonlinear Meissner effect unobservable?"

TL;DR

This paper refutes a recent claim that nonlocal effects prevent observing the nonlinear Meissner effect in YBCO, arguing instead that measurement issues or other factors are responsible for null results.

Contribution

It clarifies the role of nonlocal effects in the nonlinear Meissner effect and challenges prior assertions about their observability in YBCO.

Findings

Nonlocal effects do not prevent observing the nonlinear Meissner effect in YBCO.

Null results are likely due to measurement issues or other factors.

The nonlinear transverse magnetic moment can be observed despite nonlocal effects.

Abstract

In a recent Letter (Phys. Rev. Lett. 81, p.5640 (1998), cond-mat/9808249 v3), it was suggested that nonlocal effects may prevent observation of the nonlinear Meissner effect in YBCO. We argue that this claim is incorrect with regards to measurements of the nonlinear transverse magnetic moment, and that the most likely reason for a null result lies elsewhere.