The Peak effect anomaly in Low and High Tc superconductors : stable and metaestables vortex lattice configurations

V. BEKERIS, G. PASQUINI, D. PÉREZ DAROCA, C. CHILIOTTE AND G. LOZANO

Pittsburgh

Congreso; March Meeting 16-20 de marzo 2009, Pittsburgh; 2009

APS

Competing interactions in the vortex lattice (VL) of type II superconductors give rise to a complex phase diagram, including an order-disorder transition known as Peak Effect (PE) anomaly. The strong metastability related to the PE, masks the stationary VL configurations (VLCs), both in low and in high Tc superconductors. By means of linear ac susceptibility experiments, that avoid VL reorganization, we explore quasi-static stable and metastable states, applying different shaking protocols before measurements. In low Tc NbSe2 [1] crystals we identify T, H regions where stationary configurations  are maximally ordered (Bragg Glass), fully disordered or where ordered and disordered stable phases coexist.  In contrast, in high Tc YBa2Cu3O7-y crystals, metaestability seems to dominate and different metaestables VLCs are accessed depending on the previous dynamic history, with no access to the lowest energy configuration.  [1] G. Pasquini et al. Phys. Rev. Lett, 100, 247003 (2008).