arXiv subjects

D. Dominguez

Publications and source records attributed to D. Dominguez.

8 recordsLinked to original sources

arXiv2014

Critical behavior of spin and chiral degrees of freedom in three-dimensional disordered XY models studied by the nonequilibrium aging method

The critical behavior of the gauge-glass and the XY spin-glass models in three dimensions is studied by analyzing their nonequilibrium aging dynamics. A new numerical method, which relies on the calculation of the two-time correlation and integrated response functions, is used to determine both the critical temperature and the nonequilibrium scaling exponents, both for spin and chiral degrees of freedom. First, the ferromagnetic XY model is studied to validate this nonequilibirum aging method (NAM), since for this nondisordered system we can compare with known results obtained with standard equilibrium and nonequilibrium techniques. When applied to the case of the gauge-glass model, we show that the NAM allows us to obtain precise and reliable values of its critical quantities, improving previous estimates. The XY spin-glass model with both Gaussian and bimodal bond distributions, is analyzed in more detail. The spin and the chiral two-time correlation and integrated response functions are calculated in our simulations. The results obtained mainly for Gaussian and, to a lesser extent, for bimodal interactions, support the existence of a spin-chiral decoupling scenario, where the chiral order occurs at a finite temperature while the spin degrees of freedom order at very low or zero temperature.

cond-mat.stat-mech↗

arXiv2008

Nonequilibrium critical dynamics of the three-dimensional gauge glass

We study the non-equilibrium aging behavior of the gauge glass model in three dimensions at the critical temperature. We perform Monte Carlo simulations with a Metropolis update, and correlation and response functions are calculated for different waiting times. We obtain a multiplicative aging scaling of the correlation and response functions, calculating the aging exponent $b$ and the nonequilibrium autocorrelation decay exponent $λ_c/z_c$. We also analyze the fluctuation-dissipation relationship at the critical temperature, obtaining the critical fluctuation-dissipation ratio $X_\infty$. By comparing our results with the aging scaling reported previously for a model of interacting flux lines in the vortex glass regime, we found that the exponents for both models are very different.

cond-mat.stat-mech↗

arXiv2007

Strong Dynamical Heterogeneities in the Violation of the Fluctuation-Dissipation Theorem in Spin Glasses

We analyze numerically the violation of the fluctuation-dissipation theorem (FDT) in the $\pm J$ Edwards-Anderson (EA) spin glass model. Using single spin probability densities we reveal the presence of strong dynamical heterogeneities, which correlate with ground state information. The physical interpretation of the results shows that the spins in the EA model can be divided in two sets. In 3D, one set forms a compact structure which presents a coarsening-like behavior with its characteristic violation of the FDT, while the other asymptotically follows the FDT. Finally, we compare the dynamical behavior observed in 3D with 2D.

cond-mat.dis-nn↗

arXiv2005

Information and Topology in Attractor Neural Network

A wide range of networks, including small-world topology, can be modelled by the connectivity $γ$, and randomness $ω$ of the links. Both learning and attractor abilities of a neural network can be measured by the mutual information (MI), as a function of the load rate and overlap between patterns and retrieval states. We use MI to search for the optimal topology, for storage and attractor properties of the network. We find that, while the largest storage implies an optimal $MI(γ,ω)$ at $γ_{opt}(ω)\to 0$, the largest basin of attraction leads to an optimal topology at moderate levels of $γ_{opt}$, whenever $0\leqω<0.3$. This $γ_{opt}$ is related to the clustering and path-length of the network. We also build a diagram for the dynamical phases with random and local initial overlap, and show that very diluted networks lose their attractor ability.

cond-mat.dis-nn↗

arXiv2000

Transport properties and structures of vortex matter in layered superconductors

In this paper we analyze the structure, phase transitions and some transport properties of the vortex system when the external magnetic field lies parallel to the planes in layered superconductors. We show that experimental results for resistivity are qualitatively consistent with numerical simulations that describe the melting of a commensurate rotated lattice. However for some magnetic fields, the structure factor indicates the occurrence of smectic peaks at an intermediate temperature regime.

cond-mat.supr-con↗

arXiv2000

Driven vortices in 3D layered superconductors: Dynamical ordering along the c-axis

We study a 3D model of driven vortices in weakly coupled layered superconductors with strong pinning. Above the critical force $F_c$, we find a plastic flow regime in which pancakes in different layers are uncoupled, corresponding to a pancake gas. At a higher $F$, there is an ``smectic flow'' regime with short-range interlayer order, corresponding to an entangled line liquid. Later, the transverse displacements freeze and vortices become correlated along the c-axis, resulting in a transverse solid. Finally, at a force $F_s$ the longitudinal displacements freeze and we find a coherent solid of rigid lines.

cond-mat.supr-con↗

arXiv2000

Orientational pinning and transverse voltage: Simulations and experiments in square Josephson junction arrays

We study the dependence of the transport properties of square Josephson Junctions arrays with the direction of the applied dc current, both experimentally and numerically. We present computational simulations of current-voltage curves at finite temperatures for a single vortex in the array ($Ha^2/Φ_0=f=1/L^2$), and experimental measurements in $100\times1000$ arrays under a low magnetic field corresponding to $f\approx0.02$. We find that the transverse voltage vanishes only in the directions of maximum symmetry of the square lattice: the [10] and [01] direction (parallel bias) and the [11] direction (diagonal bias). For orientations different than the symmetry directions, we find a finite transverse voltage which depends strongly on the angle $ϕ$ of the current. We find that vortex motion is pinned in the [10] direction ($ϕ=0$), meaning that the voltage response is insensitive to small changes in the orientation of the current near $ϕ=0$. We call this phenomenon orientational pinning. This leads to a finite transverse critical current for a bias at $ϕ=0$ and to a transverse voltage for a bias at $ϕ\not=0$. On the other hand, for diagonal bias in the [11] direction the behavior is highly unstable against small variations of $ϕ$, leading to a rapid change from zero transverse voltage to a large transverse voltage within a few degrees. This last behavior is in good agreement with our measurements in arrays with a quasi-diagonal current drive.

cond-mat.supr-con↗

arXiv1997

Dynamics of d-wave Vortices: Angle-Dependent Nonlinear Hall Effect

We study the dynamics of vortices in d-wave superconductors using a phenomenological time-dependent Ginzburg-Landau equation with mixing of s- and d-wave components. We present numerical simulations under an external driving current $J$ oriented with an angle $ϕ$ with respect to the $b$ crystal axis, calculating the vortex motion and induced electric fields for $κ=\infty$. We find an intrinsic Hall effect for $ϕ\neq 0$ which depends as $\sim\sin(4ϕ)$, and increases non-linearly with $J$.

cond-mat.supr-con↗