Multiband superconductivity in V$_3$Si determined from studying the response to controlled disorder
Résumé
The London penetration depth λ(T ) was measured in a single crystal of V3Si. The superfluid density obtained
from this measurement shows a distinct signature of two almost decoupled superconducting gaps. This alone
is insufficient to distinguish between s± and s++ pairing states, but it can be achieved by studying the effect of
controlled nonmagnetic disorder on the superconducting transition temperature Tc. For this purpose, the same
V3Si crystal was sequentially irradiated by 2.5-MeV electrons three times, repeating the measurement between
the irradiation runs. A total dose of 10 C/cm2 (6.24 × 1019 electrons/cm2) was accumulated, for which Tc
changed from 16.4 K in a pristine state to 14.7 K (9.3%). Not only is this substantial suppression impossible for
a single isotropic gap, but also it is not large enough for a sign-changing s± pairing state. Our electronic band
structure calculations show how five bands crossing the Fermi energy can be naturally grouped to support two
effective gaps, not dissimilar from the physics of iron pnictides. We analyze the results using two-gap models for
both λ(T ) and Tc which describe the data very well. Thus the experimental results and theoretical analysis provide
strong support for an s++ superconductivity with two unequal gaps, 1(0) ≈ 2.53 meV and 2 (0) ≈ 1.42 meV,
and a very weak interband coupling in the V3Si superconductor.
Origine :
Fichiers éditeurs autorisés sur une archive ouverte
Loading...