Stable and metastable vortex lattice configurations throughout the Peak effect

V. BEKERIS, D. PÉREZ DAROCA, C. CHILOTTE AND G. PASQUINI

Side, Turquía

Conferencia; International Conference in Superconductivity and Magnetism; 2008

Complex systems, where order-disorder interactions compete, may be investigated by studying the vortex lattice in superconductors.  It is commonly accepted that the peak effect PE (an anomalous non-monotonous dependence of the critical current density Jc with both temperature and magnetic field) is a consequence of an order-disorder transition in the vortex lattice. However, the underlying physics of the transition, its connection with a clean limit melting transition and the stability of ordered and disordered domains throughout the vortex lattice phase diagram are issues that remain unsolved. While increasing amount of experimental evidence suggests that the nature of the PE could depend on the various materials, the marked metastability and history effects are common facts reported both in low and high Tc materials. In this work, we explore the vortex lattice configuration (VLC) landscape at each temperature (field) using a technique that excludes current induced vortex lattice reorganization. By means of linear ac susceptibility experiments in the Campbell regime, where vortices are forced to oscillate (harmonically) around their effective pinning potentials, we explore quasi-static stable and metastable VLCs following different “shaking” protocols.  Results obtained  in NbSe2 and YBCO single crystals are presented and compared. Very salient differences indicate that different physics governs the PE phenomena in both cases.