Rogelio Diaz-Mendez - Profile on Academia.edu (original) (raw)
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Papers by Rogelio Diaz-Mendez
Physical Review Letters, 2017
At low enough temperatures and high densities, the equilibrium configuration of an ensemble of ul... more At low enough temperatures and high densities, the equilibrium configuration of an ensemble of ultrasoft particles is a self-assembled, ordered, cluster-crystal. In the present work we explore the out-of-equilibrium dynamics for a two-dimensional realisation, which is relevant to superconducting materials with multi-scale intervortex forces. We find that for small temperatures following a quench, the suppression of the thermally-activated particle hopping hinders the ordering. This results in a glass transition for a monodispersed ensemble, for which we derive a microscopic explanation in terms of an "effective polydispersity" induced by multi-scale interactions. This demonstrates that a vortex glass can form in clean systems of thin films of "type-1.5" superconductors. An additional setup to study this physics can be layered superconducting systems, where the shape of the effective vortex-vortex interactions can be engineered.
International Game Theory Review, 2016
A checkers-like model game with a simplified set of rules is studied through extensive simulation... more A checkers-like model game with a simplified set of rules is studied through extensive simulations of agents with different expertise and strategies. The introduction of complementary strategies, in a quite general way, provides a tool to mimic the basic ingredients of a wide scope of real games. We find that only for the player having the higher offensive expertise (the dominant player), maximizing the offensive always increases the probability to win. For the nondominant player, interestingly, a complete minimization of the offensive becomes the best way to win in many situations, depending on the relative values of the defense expertise. Further simulations on the interplay of defense expertise were done separately, in the context of a fully offensive scenario, offering a starting point for analytical treatments. In particular, we established that in this scenario the total number of moves is defined only by the player with the lower defensive expertise. We believe that these res...
Physical Review E, 2015
We study the phases and dynamics of a gas of monodisperse particles interacting via soft-core pot... more We study the phases and dynamics of a gas of monodisperse particles interacting via soft-core potentials in two spatial dimensions, which is of interest for soft-matter colloidal systems and quantum atomic gases. Using exact theoretical methods, we demonstrate that the equilibrium lowtemperature classical phase simultaneously breaks continuous translational symmetry and dynamic space-time homogeneity, whose absence is usually associated with out-of-equilibrium glassy phenomena. This results in an exotic self-assembled cluster crystal with coexisting liquid-like long-time dynamical properties, which corresponds to a classical analog of supersolid behavior. We demonstrate that the effects of quantum fluctuations and bosonic statistics on cluster-glassy crystals are separate and competing: zero-point motion tends to destabilize crystalline order, which can be restored by bosonic statistics.
European Journal of Physics
The aim of this work is to present a formulation to solve the one-dimensional Ising model using t... more The aim of this work is to present a formulation to solve the one-dimensional Ising model using the elementary technique of mathematical induction. This formulation is physically clear and leads to the same partition function form as the transfer matrix method, which is a common subject in the introductory courses of statistical mechanics. In this way our formulation is a useful tool to complement the traditional more abstract transfer matrix method. The method can be straightforwardly generalized to other short-range chains, coupled chains and is also computationally friendly. These two approaches provide a more complete understanding of the system, and therefore our work can be of broad interest for undergraduate teaching in statistical mechanics.
Arxiv preprint arXiv:1012.4780, 2010
Abstract: We solve analytically the Langevin dynamics of the classic spherical model considering ... more Abstract: We solve analytically the Langevin dynamics of the classic spherical model considering the ferromagnetic exchange and a long-range antiferromagnetic interaction. Our results in the asymptotic regime, shows an equivalence in the functionality of the spatial ...
The European Physical Journal B, 2011
We study the Langevin dynamics of a ferromagnetic Ginzburg-Landau Hamiltonian with a competing lo... more We study the Langevin dynamics of a ferromagnetic Ginzburg-Landau Hamiltonian with a competing long-range repulsive term in the presence of an external magnetic field. The model is analytically solved within the self consistent Hartree approximation for two different initial conditions: disordered or zero field cooled (ZFC), and fully magnetized or field cooled (FC). To test the predictions of the approximation we develop a suitable numerical scheme to ensure the isotropic nature of the interactions. Both the analytical approach and the numerical simulations of two-dimensional finite systems confirm a simple aging scenario at zero temperature and zero field. At zero temperature a critical field hc is found below which the initial conditions are relevant for the long time dynamics of the system. For h < hc a logarithmic growth of modulated domains is found in the numerical simulations but this behavior is not captured by the analytical approach which predicts a t 1/2 growth law at T = 0.
Journal of Magnetism and Magnetic Materials, 2012
The dynamical properties of a 2D Heisenberg model with dipolar interactions and perpendicular ani... more The dynamical properties of a 2D Heisenberg model with dipolar interactions and perpendicular anisotropy are studied using Monte Carlo simulations in two different ordered regions of the equilibrium phase diagram. We find a temperature defining a dynamical transition below which the relaxation suddenly slows down and the system aparts from the typical Arrhenius relaxation to a Vogel-Fulcher-Tamann law. This anomalous behavior is observed in the scaling of the magnetic relaxation and may eventually lead to a freezing of the system. Through the analysis of the domain structures we explain this behavior in terms of the domains dynamics. Moreover, we calculate the energy barriers distribution obtained from the data of the magnetic viscosity. Its shape supports our comprehension of both, the Vogel-Fulcher-Tamann dynamical slowing down and the freezing mechanism.
physica status solidi (b), 2012
Phone: The behavior of the dielectric response in relaxor ferroelectric materials is studied by m... more Phone: The behavior of the dielectric response in relaxor ferroelectric materials is studied by means of Monte Carlo simulations of a simple two-dimensional (2D) generic model. It is showed that the shifting with the frequency of the peak of the temperature dependence of the dielectric permittivity e can be obtained just by considering a randomly distributed pinning anisotropy for the out-plane projection of the polar nanoregions. It is also showed that the consideration of a weak long-range dipolar interaction between nanodomains continuously drives the system to a non-relaxor ferroelectric state in which a single peak is observed for the dielectric permittivity.
Physical Review B, 2010
We explore the equilibrium properties of a two-dimensional Ising spin model with short-range exch... more We explore the equilibrium properties of a two-dimensional Ising spin model with short-range exchange and long-range dipolar interactions as a function of the applied magnetic field H. The model is studied through extensive Monte Carlo simulations that show the existence of many modulated phases with long range orientational order for a wide range of fields. These phases are characterized by different wave vectors that change discontinuously with the magnetic field. We provide numerical evidence supporting the existence of first order transitions between these phases. At higher fields our results suggest a Kosterliz-Thouless scenario for the transition from a bubble to a ferromagnetic phase.
Monte Carlo simulations of the equilibrium and non-equilibrium properties of low-dimensional magnetic systems with long-range dipolar interactions
Journal of Magnetism and Magnetic Materials, 2005
The equilibrium and non-equilibrium properties of a two-dimensional Ising-like spin system with b... more The equilibrium and non-equilibrium properties of a two-dimensional Ising-like spin system with both ferromagnetic exchange and long-range dipolar interactions are studied. Implementing the Ewald Sums (ES) for the calculation of the dipolar interaction we reproduced the results of the literature concerning the equilibrium-phase diagram and the stability of the phases. We also investigated the aging regime and the Fluctuation–Dissipation Theorem
Arxiv preprint arXiv: …, 2010
Alejandro Mendoza-Coto,1,2 Rogelio Díaz-Méndez,3,2 Roberto Mulet,1, 2 Lucas Nicolao,4 and Daniel ... more Alejandro Mendoza-Coto,1,2 Rogelio Díaz-Méndez,3,2 Roberto Mulet,1, 2 Lucas Nicolao,4 and Daniel A. Stariolo5 1Department of Theoretical Physics, Physics Faculty, University of Havana, La Habana, CP 10400, Cuba 2Henri-Poincaré-Group of Complex Systems, ...
Physical Review Letters, 2017
At low enough temperatures and high densities, the equilibrium configuration of an ensemble of ul... more At low enough temperatures and high densities, the equilibrium configuration of an ensemble of ultrasoft particles is a self-assembled, ordered, cluster-crystal. In the present work we explore the out-of-equilibrium dynamics for a two-dimensional realisation, which is relevant to superconducting materials with multi-scale intervortex forces. We find that for small temperatures following a quench, the suppression of the thermally-activated particle hopping hinders the ordering. This results in a glass transition for a monodispersed ensemble, for which we derive a microscopic explanation in terms of an "effective polydispersity" induced by multi-scale interactions. This demonstrates that a vortex glass can form in clean systems of thin films of "type-1.5" superconductors. An additional setup to study this physics can be layered superconducting systems, where the shape of the effective vortex-vortex interactions can be engineered.
International Game Theory Review, 2016
A checkers-like model game with a simplified set of rules is studied through extensive simulation... more A checkers-like model game with a simplified set of rules is studied through extensive simulations of agents with different expertise and strategies. The introduction of complementary strategies, in a quite general way, provides a tool to mimic the basic ingredients of a wide scope of real games. We find that only for the player having the higher offensive expertise (the dominant player), maximizing the offensive always increases the probability to win. For the nondominant player, interestingly, a complete minimization of the offensive becomes the best way to win in many situations, depending on the relative values of the defense expertise. Further simulations on the interplay of defense expertise were done separately, in the context of a fully offensive scenario, offering a starting point for analytical treatments. In particular, we established that in this scenario the total number of moves is defined only by the player with the lower defensive expertise. We believe that these res...
Physical Review E, 2015
We study the phases and dynamics of a gas of monodisperse particles interacting via soft-core pot... more We study the phases and dynamics of a gas of monodisperse particles interacting via soft-core potentials in two spatial dimensions, which is of interest for soft-matter colloidal systems and quantum atomic gases. Using exact theoretical methods, we demonstrate that the equilibrium lowtemperature classical phase simultaneously breaks continuous translational symmetry and dynamic space-time homogeneity, whose absence is usually associated with out-of-equilibrium glassy phenomena. This results in an exotic self-assembled cluster crystal with coexisting liquid-like long-time dynamical properties, which corresponds to a classical analog of supersolid behavior. We demonstrate that the effects of quantum fluctuations and bosonic statistics on cluster-glassy crystals are separate and competing: zero-point motion tends to destabilize crystalline order, which can be restored by bosonic statistics.
European Journal of Physics
The aim of this work is to present a formulation to solve the one-dimensional Ising model using t... more The aim of this work is to present a formulation to solve the one-dimensional Ising model using the elementary technique of mathematical induction. This formulation is physically clear and leads to the same partition function form as the transfer matrix method, which is a common subject in the introductory courses of statistical mechanics. In this way our formulation is a useful tool to complement the traditional more abstract transfer matrix method. The method can be straightforwardly generalized to other short-range chains, coupled chains and is also computationally friendly. These two approaches provide a more complete understanding of the system, and therefore our work can be of broad interest for undergraduate teaching in statistical mechanics.
Arxiv preprint arXiv:1012.4780, 2010
Abstract: We solve analytically the Langevin dynamics of the classic spherical model considering ... more Abstract: We solve analytically the Langevin dynamics of the classic spherical model considering the ferromagnetic exchange and a long-range antiferromagnetic interaction. Our results in the asymptotic regime, shows an equivalence in the functionality of the spatial ...
The European Physical Journal B, 2011
We study the Langevin dynamics of a ferromagnetic Ginzburg-Landau Hamiltonian with a competing lo... more We study the Langevin dynamics of a ferromagnetic Ginzburg-Landau Hamiltonian with a competing long-range repulsive term in the presence of an external magnetic field. The model is analytically solved within the self consistent Hartree approximation for two different initial conditions: disordered or zero field cooled (ZFC), and fully magnetized or field cooled (FC). To test the predictions of the approximation we develop a suitable numerical scheme to ensure the isotropic nature of the interactions. Both the analytical approach and the numerical simulations of two-dimensional finite systems confirm a simple aging scenario at zero temperature and zero field. At zero temperature a critical field hc is found below which the initial conditions are relevant for the long time dynamics of the system. For h < hc a logarithmic growth of modulated domains is found in the numerical simulations but this behavior is not captured by the analytical approach which predicts a t 1/2 growth law at T = 0.
Journal of Magnetism and Magnetic Materials, 2012
The dynamical properties of a 2D Heisenberg model with dipolar interactions and perpendicular ani... more The dynamical properties of a 2D Heisenberg model with dipolar interactions and perpendicular anisotropy are studied using Monte Carlo simulations in two different ordered regions of the equilibrium phase diagram. We find a temperature defining a dynamical transition below which the relaxation suddenly slows down and the system aparts from the typical Arrhenius relaxation to a Vogel-Fulcher-Tamann law. This anomalous behavior is observed in the scaling of the magnetic relaxation and may eventually lead to a freezing of the system. Through the analysis of the domain structures we explain this behavior in terms of the domains dynamics. Moreover, we calculate the energy barriers distribution obtained from the data of the magnetic viscosity. Its shape supports our comprehension of both, the Vogel-Fulcher-Tamann dynamical slowing down and the freezing mechanism.
physica status solidi (b), 2012
Phone: The behavior of the dielectric response in relaxor ferroelectric materials is studied by m... more Phone: The behavior of the dielectric response in relaxor ferroelectric materials is studied by means of Monte Carlo simulations of a simple two-dimensional (2D) generic model. It is showed that the shifting with the frequency of the peak of the temperature dependence of the dielectric permittivity e can be obtained just by considering a randomly distributed pinning anisotropy for the out-plane projection of the polar nanoregions. It is also showed that the consideration of a weak long-range dipolar interaction between nanodomains continuously drives the system to a non-relaxor ferroelectric state in which a single peak is observed for the dielectric permittivity.
Physical Review B, 2010
We explore the equilibrium properties of a two-dimensional Ising spin model with short-range exch... more We explore the equilibrium properties of a two-dimensional Ising spin model with short-range exchange and long-range dipolar interactions as a function of the applied magnetic field H. The model is studied through extensive Monte Carlo simulations that show the existence of many modulated phases with long range orientational order for a wide range of fields. These phases are characterized by different wave vectors that change discontinuously with the magnetic field. We provide numerical evidence supporting the existence of first order transitions between these phases. At higher fields our results suggest a Kosterliz-Thouless scenario for the transition from a bubble to a ferromagnetic phase.
Monte Carlo simulations of the equilibrium and non-equilibrium properties of low-dimensional magnetic systems with long-range dipolar interactions
Journal of Magnetism and Magnetic Materials, 2005
The equilibrium and non-equilibrium properties of a two-dimensional Ising-like spin system with b... more The equilibrium and non-equilibrium properties of a two-dimensional Ising-like spin system with both ferromagnetic exchange and long-range dipolar interactions are studied. Implementing the Ewald Sums (ES) for the calculation of the dipolar interaction we reproduced the results of the literature concerning the equilibrium-phase diagram and the stability of the phases. We also investigated the aging regime and the Fluctuation–Dissipation Theorem
Arxiv preprint arXiv: …, 2010
Alejandro Mendoza-Coto,1,2 Rogelio Díaz-Méndez,3,2 Roberto Mulet,1, 2 Lucas Nicolao,4 and Daniel ... more Alejandro Mendoza-Coto,1,2 Rogelio Díaz-Méndez,3,2 Roberto Mulet,1, 2 Lucas Nicolao,4 and Daniel A. Stariolo5 1Department of Theoretical Physics, Physics Faculty, University of Havana, La Habana, CP 10400, Cuba 2Henri-Poincaré-Group of Complex Systems, ...