Quenching quantum vortex fluctuations in order to achieve higher critical current densities in MBa2Cu3Ox coated conductors

The relationship between the issue of obtaining higher critical current densities in textured MBa2Cu3O7 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 Hg(T) depends upon three parameters, a quantum fluctuation parameter Q, the Lindemann number cL, 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 Hg(T) lines of YBa2Cu3Ox with various levels of Pr, Ca, and oxygen doping.