arXiv subjects

Alejandro Kolton

Publications and source records attributed to Alejandro Kolton.

6 recordsLinked to original sources

arXiv2023

Disordered hyperuniform vortex matter with rhombic distortions in FeSe at low fields

In the current quest to synthesize hyperuniform materials with interesting applications, addressing the coupling of the objects composing the system to the physical properties of the host medium is crucial. With this aim we study a model system: vortices in the FeSe superconductor subject to a considerable magneto-elastic coupling with the host sample. We reveal that the low-field FeSe vortex structure is of the weakest hyperuniform type possibly due to the relevance of the anisotropic and long-ranged interaction term introduced by the magneto-elastic coupling. This work indicates that it is possible to tailor the hyperuniformity class of material systems by tuning the coupling of interacting objects with elastic properties of the host medium.

cond-mat.supr-con↗

arXiv2018

Pinning of Domain Walls in thin Ferromagnetic Films

We present a quantitative investigation of magnetic domain wall pinning in thin magnets with perpendicular anisotropy. A self-consistent description exploiting the universal features of the depinning and thermally activated sub-threshold creep regimes observed in the field driven domain wall velocity, is used to determine the effective pinning parameters controlling the domain wall dynamics: the effective height of pinning barriers, the depinning threshold, and the velocity at depinning. Within this framework, the analysis of results published in the literature allows for a quantitative comparison of pinning properties for a set of magnetic materials in a wide temperature range. On the basis of scaling arguments, the microscopic parameters controlling the pinning: the correlation length of pinning, the collectively pinned domain wall length (Larkin length) and the strength of pinning disorder, are estimated from the effective pinning and the micromagnetic parameters. The analysis of thermal effects reveals a crossover between different pinning length scales and strengths at low reduced temperature.

cond-mat.mes-hall↗

arXiv2017

Universal Depinning Transition of Domain Walls in Ultrathin Ferromagnets

We present a quantitative and comparative study of magnetic field driven domain wall depinning transition in different ferromagnetic ultrathin films over a wide range of temperature. We reveal a universal scaling function accounting for both drive and thermal effects on the depinning transition, including critical exponents. The consistent description we obtain for both the depinning and subthreshold thermally activated creep motion should shed light on the universal glassy dynamics of thermally fluctuating elastic objects pinned by disordered energy landscapes.

cond-mat.dis-nn↗

arXiv2016

Universal pinning energy barrier for driven domain walls in thin ferromagnetic films

We report a comparative study of magnetic field driven domain wall motion in thin films made of different magnetic materials for a wide range of field and temperature. The full thermally activated creep motion, observed below the depinning threshold, is shown to be described by a unique universal energy barrier function. Our findings should be relevant for other systems whose dynamics can be modeled by elastic interfaces moving on disordered energy landscapes.

cond-mat.mes-hall↗

arXiv2005

Non-equilibrium relaxation of an elastic string in a random potential

We study the non--equilibrium motion of an elastic string in a two dimensional pinning landscape using Langevin dynamics simulations. The relaxation of a line, initially flat, is characterized by a growing length, $L(t)$, separating the equilibrated short length scales from the flat long distance geometry that keep memory of the initial condition. We show that, in the long time limit, $L(t)$ has a non--algebraic growth with a universal distribution function. The distribution function of waiting times is also calculated, and related to the previous distribution. The barrier distribution is narrow enough to justify arguments based on scaling of the typical barrier.

cond-mat.dis-nn↗

arXiv2003

Transverse phase-locking in fully frustrated Josephson junction arrays: a new type of fractional giant steps

We study, analytically and numerically, phase locking of driven vortex lattices in fully-frustrated Josephson junction arrays at zero temperature. We consider the case when an ac current is applied {\it perpendicular} to a dc current. We observe phase locking, steps in the current-voltage characteristics, with a dependence on external ac-drive amplitude and frequency qualitatively different from the Shapiro steps, observed when the ac and dc currents are applied in parallel. Further, the critical current increases with increasing transverse ac-drive amplitude, while it decreases for longitudinal ac-drive. The critical current and the phase-locked current step width, increase quadratically with (small) amplitudes of the ac-drive. For larger amplitudes of the transverse ac-signal, we find windows where the critical current is hysteretic, and windows where phase locking is suppressed due to dynamical instabilities. We characterize the dynamical states around the phase-locking interference condition in the $IV$ curve with voltage noise, Lyapunov exponents and Poincaré sections. We find that zero temperature phase-locking behavior in large fully frustrated arrays is well described by an effective four plaquette model.

cond-mat.supr-con↗