Observation of the crossover from two-gap to single-gap superconductivity through specific heat measurements in neutron-irradiated MgB2.
We report specific heat measurements on neutron-irradiated MgB2 samples, for which the critical temperature is lowered to 8.7 K, but the superconducting transition remains extremely sharp, indicative of a defect structure extremely homogeneous. Our results evidence the presence of two superconducting gaps in the temperature range above 21 K, while single-gap superconductivity is well established as a bulk property, not associated with local disorder fluctuations, when Tc decreases to 11 K.
Putti
M
M
CNR-INFM-LAMIA, Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
Affronte
M
M
Ferdeghini
C
C
Manfrinetti
P
P
Tarantini
C
C
Lehmann
E
E