The European Physical Journal B最新文献

We analyze charge and field equilibrium distributions in an insulating medium with ions confined by two flat adsorbing–desorbing electrodes without an external electric field. The equilibrium charge density profile of the sample is determined by considering the accumulation of mobile charges at the surface, which generates a surface electric potential. Charging dynamics are explored using a kinetic balance equation, resulting in a time-dependent net charge surface and an inhomogeneous Volterra integral equation of the second kind, and determining the surface electric potential in the half-space approximation. The results show a non-monotonic time dependence for the surface electric potential due to adsorption–desorption processes. The analysis is extended to a finite sample and reveals the presence of a maximum in the time behavior of difference of potential when only one type of ion is selectively adsorbed. The trend is instead monotonic when one electrode only adsorbs positive, and the other one adsorbs only negative ions. This approach may be used as a convenient theoretical tool for further investigation of charge accumulation on the surfaces of electrolytic cells.

We consider a spinless t-(t') ionic Hubbard chain at 1/2 filling and large hopping ratio (t'/t). In this limit, the model adequately maps onto a weakly coupled triangular ladder with a potential interchain bias. The low-energy properties of the system are formed due to the interplay of geometrical frustration, correlations and charge imbalance. We derive the effective field-theoretical model to study universal properties of the model in the scaling limit. We show that at full dynamical frustration, the ground state of the ladder represents a repulsive version of the Luther–Emery liquid with dominant orbital antiferromagnetic correlations exhibiting the slowest power law decay in the ground state. Pairing correlations also display algebraic order but are subdominant. At an incomplete dynamical frustration, a finite commensurability gap is dynamically generated, and the fluctuating OAF transforms to a long-range ordered state with a spontaneously broken time-reversal symmetry. The mass gap in the spectrum of relative density fluctuations gets suppressed upon increasing the potential bias.

Biological information processing pathways in neuron assemblies rely on spike activity, encoding information in the time domain, and operating the highly parallel network at an outstanding robustness and efficiency. One particularly important aspect is the distributed, local pre-processing effectively converting stimulus-induced signals to action potentials, temporally encoding analog information. The field of brain-inspired electronics strives to adapt concepts of information processing in neural networks, e.g., stimulus detection and processing being intertwined. As such, stimulus-modulated resistive switching in memristive devices attracts an increasing attention. This work reports on a three-component memsensor circuit, featuring a UV-sensor, a memristive device with diffusive switching characteristics and a capacitor. Upon application of a DC bias, complex, stimulus-dependent spiking and brain-inspired bursting can be observed, as experimentally showcased using combination of a microstructured, tetrapodal ZnO sensor and a Au/SiO_xN_y/Ag cross-point memristive device. The experimental findings are corroborated by a wave digital model, which successfully replicates both types of behavior and outlines the relation of temporal variation of switching thresholds to the occurrence of bursting activity.

In addressing the complexity inherent in comparing socioeconomic indicators across diverse countries, a substantial barrier arises from the wide array of distinct calculation approaches. Consequently, a highly pertinent question emerges: how does one compare values when the underlying calculation methodologies are diverse? In this context, we propose a multidisciplinary and heterogeneous approach, employing numerical and visual comparisons to analyze socioeconomic indicators of municipalities in the US, Brazil and other Latin American countries. We identify independent-scale patterns in three stages: initially, by compiling a database sourced from respected institutions in each country and identifying correlations within this dataset; next, by creating graphical representations using a binning methodology for scatter plots of the identified patterns; finally, by transforming the dispersions from the initial stage into graphs using a variant of the Gravitational Clustering Algorithm technique from astrophysics. We find significant relationships, specifically in the logarithmic relationship between Municipal HDI and population size. In some countries, global minima were identified, suggesting the existence of a critical population density at which municipalities above this threshold exhibit a positive and significant correlation with an increase in their HDI.

We theoretically investigate spin photo-currents in two types of antiferromagnetic insulators with Dzyaloshinskii–Moriya (DM) interactions: one with staggered DM interactions and the other with uniform DM interactions. The magnon spectrum for each system thus becomes asymmetric with respect to the propagation direction of magnons, which may be utilized to enhance the nonlinear spin conductivity. Indeed, we show that the spin conductivity in each system could be up to the order of 10 nJ/((textrm{cm}^2cdot textrm{T}^2)) when the system is coupled to an AC magnetic field transverse to the ordered spins. Due to the special magnon dispersion, however, an extra static field is required to achieve a high conductivity in the system with staggered DM interactions. The results could be useful in opto-spintronics based on magnetic excitations.

The concept of dynamical freezing is a phenomenon where a suitable set of local observables freezes under a strong periodic drive in a quantum many-body system. This happens because of the emergence of approximate but perpetual conservation laws when the drive is strong enough. In this work, we probe the resilience of dynamical freezing to random perturbations added to the relative phases between the interfering states (elements of a natural basis) in the time-evolving wave function after each drive cycle. We study this in an integrable Ising chain in a time-periodic transverse field. Our key finding is, that the imprinted phase noise melts the dynamically frozen state, but the decay is “slow”: a stretched-exponential decay rather than an exponential one. Stretched-exponential decays (also known as Kohlrausch relaxation) are usually expected in complex systems with time-scale hierarchies due to strong disorders or other inhomogeneities resulting in jamming, glassiness, or localization. Here we observe this in a simple translationally invariant system dynamically frozen under a periodic drive. Moreover, the melting here does not obliterate the entire memory of the initial state but leaves behind a steady remnant that depends on the initial conditions. This underscores the stability of dynamically frozen states.