Josephson plasma resonance in solid and glass phases of Bi 2Sr 2CaCu 2O 8+ δ

Abstract

Vortex matter phases and phase transitions are investigated by means of Josephson plasma resonance in under-doped Bi 2Sr 2CaCu 2O 8+ δ single crystals in a microwave frequency range between 19 and 70 GHz. Accompanied by the vortex lattice melting transition, a jump of the interlayer phase coherence extracted from the field dependence of the plasma frequency was observed. In the solid phase, the interlayer coherence little depends on field at a temperature region well below T c while it gradually decreases as field increases toward the melting line up to just below T c. As a result, the magnitude 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 becomes weak especially just below T c.