Observation of the ghost critical field for superconducting fluctuations in a disordered TaN thin film
Physical Review B 88 (2013) 223
Abstract
We experimentally study the ghost critical field (GCF), a magnetic field scale for the suppression of superconducting fluctuations, using Hall effect and magnetoresistance measurements on a disordered superconducting thin film near its transition temperature ( T_c ). We observe an increase in the Hall effect with a maximum in field that tracks the upper critical field below ( T_c ), vanishes near ( T_c ), and returns to higher fields above ( T_c ). Such a maximum has been observed in studies of the Nernst effect and identified as the GCF. Magnetoresistance measurements near Tc indicate quenching of superconducting fluctuations, agree with established theoretical descriptions, and allow us to extract the GCF and other parameters. Above ( T_c ), the Hall peak field is quantitatively distinct from the GCF, and we contrast this finding with ongoing studies of the Nernst effect and superconducting fluctuations in unconventional and thin-film superconductors.