Je. Eldridge et al., FAR-INFRARED MAGNETOCONDUCTIVITY OF A HIGH-T-C SUPERCONDUCTING FILM, Physical review. B, Condensed matter, 52(6), 1995, pp. 4462-4466
Measurements of the far-infrared reflectivity R of a superconducting Y
Ba2Cu3O7 thin film exhibit a strong dependence on magnetic field B. Th
e ratios of R (B)/R(O) were used, in conjunction with a separate measu
rement of R (O), to obtain the absolute values of R (B). A Kramers-Kro
nig analysis then gave the field-dependent conductivity which shows a
broad resonance between 50 and 250 cm(-1). A theory involving vortex m
otion with pinning was able to fit the shape of the field-dependent co
nductivity resonance but not the magnitude.