Superconducting Transition Induced by Columnar Disorder in Strong Magnetic Field

Abstract

The problem of superconducting transition in the magnetic field in presence of strong disorder has been a subject of great interest in recent years. From the point of view of applications. there is a need to know how to introduce defects into a superconducting material in a way that would maximize pinning of vortices and therefore increase critical currents [1] On the theoretical side, understanding of the phase transitions in presence of quenched disorder and description of the low-temperature disordered phases have always been challenging problems. and often required novel physical concepts and mathematical techniques. A prime example of this is the theory of spin glasses. For the superconducting transition in the magnetic field. a variety of novel low-temperature phases have been proposed. differing iii the cases of point like [2, 3] and line-like disorder [4, 5. 6]. In the present paper we discuss a theory of superconducting transition at high magnetic fields in presence of columnar (line-like) defects [6]. We have in mind a three-dimensiorral. anisotropic, strongly type-II superconductor (YBCO. for example) in typical magnetic fields of ∼ 1T, irradiated by a flux of some heavy ions with energies ∼ 1GeV and with trajectories parallel to the external magnetic field. If the thickness of the sample in the direction of the beam is ∼ 10μm. the ions are able to penetrate through the entire material. leaving behind the continuous tracks of damaged superconductor of diameter d ∼ 50A.