Comment on "precision global measurements of London penetration depth in FeTe 0.58Se 0.42"

Abstract

Cho have reported on the temperature dependence of the London penetration depth deduced from tunnel diode oscillator (TDO) measurements in optimally doped Fe(Se,Te) single crystals. According to their analysis, these measurements could suggest a nodeless two-gap pairing symmetry with strong pair-breaking effects. However, to reach this conclusion, the authors fit the temperature dependence of the superfluid density with a two band clean limit model, which is incompatible with the presence of strong pair-breaking effects, deduced from the Tn temperature dependence of the London penetration depth below T c/3. Moreover, they claim that their results are also ruling out the suggestion that surface conditions can significantly affect the TDO data, but this conclusion is based on one very specific damaging process and completely ignores the large dispersion in the previously published TDO data. © 2012 American Physical Society.