Vortex matter in high-temperature superconductors: a model system to study phenomena related to crystalline melting and fragile glass formation?

Abstract We suggest that the vortex matter in high-temperature superconductors represents a model system to study different phenomena related to the melting of a crystalline phase, including the formation of highly fragile glass phases. A unique feature of the vortex system is that the vortex density can easily be varied over a large range by changing the applied magnetic field. The resulting vortex H – T phase diagram shows many features of the universal Tamman phase diagram for melting, including an equal entropy Kauzmann point at a pressure (field) maximum, as well as `inverse melting', which usually is believed to appear only at extremely high pressures. The thermodynamics of the liquid vortex phase, as well as the kinetics of a supercooled liquid, show extreme fragility, which may be tuned by changing the magnetic field or the crystalline disorder of the superconductor. Understanding the vortex phase diagram is, thus, expected to lead to new insights into the physics of structural glass-forming liquids and the concept of fragility.