Josephson plasma resonance in Josephson vortex states

Josephson plasma resonance of under-doped Bi2Sr2CaCu2O8+delta single crysta ls in magnetic fields parallel to the ab-plane has been studied at microwav e frequencies v between 10 and 52 GHz. Two resonance lines are discovered w ith distinctly different characters as functions of different physical para meters such as magnetic fields, microwave frequencies, temperatures, etc. T hose two resonances behave entirely differently from the ones for H//c and are attributed to the mixed resonance plasma modes with collective motion o f the Josephson vortices. (C) 2001 Elsevier Science BY. All rights reserved .