Quenching quantum vortex fluctuations in order to achieve higher critical current densities in [formula omitted] coated conductors

Abstract

The relationship between the issue of obtaining higher critical current densities in textured M Ba 2 Cu 3 O 7 films and the boundary between the electrically dissipation-less vortex solid state and the dissipative vortex liquid state is explored in the context of a recently developed phenomenological melting line expression. Based on an extension of the Lindemann melting theory of Blatter and Ivlev, the temperature-field H – T dependence of this expression for H g ( T ) depends upon three parameters, a quantum fluctuation parameter Q, the Lindemann number c L , and an exponent s, for which the value of each is relevant to understanding the problem of increasing the critical current density over an extended H – T region. The importance of minimizing the value of the quantum parameter Q as a means of achieving higher critical current densities is demonstrated by examining the H g ( T ) lines of YBa 2 Cu 3 O x with various levels of Pr, Ca, and oxygen doping.