INVITADA: AC dynamic reorganization and critical phase transition in vortex matter

V. BEKERIS; M. MARZIALI BERMÚDEZ; G. PASQUINI; M. ESKILDSEN

Beijing

Conferencia; 12th International Conference on Materials and Mechanism of Superconductivity and High Temperature Superconductors (M2S-2018); 2018

In a variety of complex systems, among witch vortex matter is a prototype, glassy behavoir and metastable configurations give rise to striking history effects closely connected with a rich dynamics where plasticity plays a key role. Superconducting materials with randomly distributed weak pinning centers are an ideal playground for research. In these systems, the stable vortex phase at low temperature and low magnetic fields is an ordered dislocation free Bragg Glass (BG). With increasing field and/or temperature, the system undergoes anorder-disorder transition to a strongly pinned disordered phase, whose fingerprint is a sudden increase in the effective pining, known as the Peak Effect (PE) anomaly. It is well known that a field-cooled vortex lattice (VL) remains trapped below the PE in a more strongly pinned disordered configuration; with the help of high dc currents or large shaking magnetic fields the system can reach the stable ordered BG, free of dislocations, which has lower effectivepinning. In this framework, the existence of a transitional region between the ordered and the disordered phases remained a controversial issues for more than a decade.In this talk I will briefly review the main results obtained in the last years by our group supporting the existence of a narrow in-between transitional regionbetween the ordered and the disordered phases, where the application of shakingAC fields gives rise to bulk VL configurations with intermediatedislocation densities correlated with intermediate effective pinning [1].Numerical simulations [2] suggested that these ?intermediate? configurations areoriginated from a VL reorganization driven by the oscillatory dynamics. Wepresent new experimental results [3] that show clear evidence of this dynamicreordering. Moreover, unambiguous signature of criticality suggests that thisreorganization is closely connected with a dynamic phase transition (Fig. 1).References[1] G. Pasquini et.al., Phys. Rev. Lett. 100, 247003 (2008); M. Marziali Bermúdez et al.,Phys. Rev. Lett. 115, 067001 (2015).[2] D. Pérez Daroca et al.; Phys. Rev. B 84, 012508 (2011).[2]M. Marziali Bermúdez and G. Pasquini, in preparation (2018).