Josephson plasma resonance in solid and glass phases of Bi2Sr2CaCu2O8+delta

Vortex matter phases and phase transitions, are investigated by means of Jo sephson plasma resonance in under-doped Bi2Sr2CaCu2O8+delta single crystals in a microwave frequency range between 19 and 70 GHz. Accompanied by the v ortex lattice melting transition, a jump of the interlayer phase coherence extracted from the field dependence of the plasma frequency was observed. I n the solid phase, the interlayer coherence little depends on field at a te mperature region well below T-c while it gradually decreases as field incre ases toward the melting line up to just below T-c. As a result, the magnitu de of the jump decreases with increasing temperature and is gradually lost in the vicinity of T-c. This indicates that the vortex lines formed in the vortex solid phase are thermally meandering and the phase transition become s weak especially just below T-c. (C) 2001 Elsevier Science B.V. All rights reserved.