Lance E. De Long
Joseph W. Brill
Zhigang Xu
Henryk Drulis
Dept. of Phys. and Astron., Univ. of Kentucky, Lexington, KY 40506-0055
Although high-temperature oxide superconductors have been studied since 1986, the static and dynamic behaviors of magnetic vortices generated by applied magnetic fields and electrical currents remain controversial. These phenomena are important for at least two reasons: (1) vortex motion generates dissipation causing degraded performance in practical superconducting devices; and (2) the high transition temperatures (T[sub c](approximately equal to)100 K), short coherence length ((less than or equal to)10 (Angstrom)) and strong crystalline anisotropy of high-T[sub c] oxides are predicted to cause novel structural rearrangements or melting transitions of the ``vortex lattice'' at temperatures T well below the superconducting/normal phase boundary H[sub c2](T). Recent mechanical oscillator studies of relatively isotropic, low-T[sub c] superconductors reveal dissipation anomalies and frequency shifts similar to those observed in high-T[sub c] materials, challenging current theories for the vortex state of superconductors. [Work supported by NSF and Research Corp.]