Comprehensive characterizing of vortex phases in type-II superconductor YBa2Cu3O7-x by a magnetoelectric technique

Superconductors (SC) have two fundamental properties, zero resistivity and perfect diamagnetism which can fully exclude small external magnetic field in principle. The m₀H field inside the SC remains zero until the superconductivity is fully destroyed when the external field H is above a critical field H_c1 in type-I SC. However, due to the negative interface energy between superconducting and normal phases, the magnetic field lager than H_c1 can sometime penetrate the SC phase instead of it in type-II SC. Above H_c1, the magnetic field enters a type II SC in the form of quantized vortices, each carrying one quantum of vortex ?₀=hc/2e, and the vortices could form regular triangular or square lattice as a two dimensional solid state. So far, one method that is relatively simple, cheap and fast, which is able to characterize the vortex phases and phase boundaries comprehensively, is still lacking.

In this work, a cheap and simple composite ME technique has been introduced to comprehensively study the vortex phases in type-II High Tc superconductor YBa2Cu3O7-x polycrystalline. We demonstrate that this method can comprehensively investigate and plot the vortex phase diagram, including the Hc1, irreversible line, Hc2 and distinguishing among vortex glass, vortex liquid, non-vortex states. Moreover, it can probe the dynamic response of vortex liquid phase under different frequency and stimulus strength. Most important, it can quantitatively measure the density of vortex in the vortex solid phase.