Vortex lock-in transition in Tl 2Ba 2CuO 6 superconductor and vortex phase diagram

Abstract

Lock-in transition in good quality over-doped Tl 2Ba 2CuO 6 crystals has been investigated. As the c-axis angle θ with the magnetic field H approaches 90°, the flux flow resistivity ρ( θ) exhibits a sharp drop, a dip and a peak. These features were observed for a particular range of H and temperatures T and they have been assigned to the vortex phase transitions of different types. These enabled us to identify the associated vortex phase diagrams, viz. the θ– t and θ– H phase diagrams, where t is the reduced temperature T/ T c We made an attempt to fit the data with the available theories and to discuss the results.