POSTER: AC dynamic reorganization and non-equilibrium phase transition in driven vortex matter

BERMÚDEZ, M. MARZIALI; G. PASQUINI

Buenos Aires

Conferencia; Statphys 2019; 2019

IUPAP

In a variety of disordered elastic media, glassy behavior and metastable configurations give rise to striking history effects closely connected with a rich dynamics where plasticity plays a key role. Driven away from equilibrium, these systems may exhibit rich features like development of self-organized configurations and an unusual dynamics, where non-equilibrium phase transitions (NEPT) is a topic of ongoing research [L. F. Cugliangolo, C. R. Phys. 14, 685 (2013)]. In particular, an amount of work have been devoted to study the phenomenon of depinning transitions under the action of a continuous driving force and their connection with a NEPT [Reichhardt et al., Rep. Prog. Phys. 80 026501, 2017]. On the other hand, the dynamics of these systems driven by alternating forces had been poorly addressed before the last decade. During the last ten years, an amount of work shown that the AC dynamics displays very particular characteristics not directly translatable from DC dynamic regimes and may produce an evolution and a particular reorganization of the systems. Vortex matter is an ideal playground for this research. Our group have been working during more than one decade in studying the AC dynamics in the vortex lattice (VL) of NbSe2 clean single crystals, a system that undergoes an order-disorder transition. By AC susceptibility and Neutron Diffraction (SANS) experiments, we obtained results supporting the existence of a narrow in-between transitional region between the ordered and the disordered phases, where the application of oscillatory AC fields gives rise to bulk VL configurations with intermediate degree of disorder, correlated with intermediate linear AC response [Pasquini et al., PRL 100, 247003 (2008); Marziali Bermúdez et al.,PRL 115, 067001 (2015)]. Numerical simulations suggested that these ?intermediate? configurations are originated from a VL reorganization driven by the oscillatory dynamics [Pérez Daroca et al.; PRB 84, 012508 (2011)].In this work, we present new experimental results that show clear evidence of this dynamic reordering. Moreover, unambiguous signature of criticality suggests that thisreorganization is closely associated with a dynamic phase transition. The connection with a critical AC depinning transition [Pérez Daroca et al.; PRB 81, 184520 (2010), Y Kawamura et al., 2017 New J. Phys. 19 093001 (2017)] is also discussed.