arXiv subjects

Vicente Delgado

Publications and source records attributed to Vicente Delgado.

6 recordsLinked to original sources

arXiv2024

Spinor Bose-Einstein condensates subject to current-density interactions

Recently achieved chiral condensates open intriguing avenues for the study of the chiral properties induced by current-density interactions. An attempt to include these features in a spinor system is presented, which gives rise to a nonlinear, effective spin-orbit coupling that emerges from the differential orbital currents, along with constraints in the conserved quantities due to the linear coupling between spin components. Chirality pervades the resulting spectrum of stationary states and their dynamical stability, which are explored in plane waves, dark and bright solitons, and Josephson vortices. Our analytical and numerical results reveal the destabilizing role of polarization and Josephson currents, and support the existence of stable nonlinear states built of linear superpositions of plane waves.

cond-mat.quant-gas↗

arXiv2023

Chiral currents in Bose-Einstein condensates subject to current-density interactions

Persistent currents in quasi-one-dimensional Bose-Einstein condensates become chiral in the presence of current-density interactions. This phenomenon is explored in ultracold atoms loaded in a rotating ring geometry, where diverse current-carrying stationary states are analytically found to generalize previously known solutions to the mean-field equations of motion. Their dynamical stability is tested by numerical simulations that show stable currents for states with both constant and modulated density profiles, while decaying currents appear only beyond a unidirectional velocity threshold. Recent experiments in the field make these states within experimental reach.

cond-mat.quant-gas↗

arXiv2012

Coupled-wave surface-impedance analysis of extraordinary transmission through single and stacked metallic screens

In this paper we present an efficient Coupled-wave surface-impedance method for the analysis of extraordinary optical transmission (EOT) through single and stacked realistic metallic screens under normal and oblique incidence, including possible dielectric interlayers. The proposed theory is valid for the complete frequency range where EOT has been reported, including microwaves and optics. Electromagnetic simulations validate the results of the model, which allows for a fast and accurate characterization of the analyzed structures.

physics.optics↗

arXiv2011

Super-resolution for a point source better than λ/500 using positive refraction

Leonhardt demonstrated (2009) that the 2D Maxwell Fish Eye lens (MFE) can perfectly focus 2D Helmholtz waves of arbitrary frequency, i.e., it can perfectly transport an outward (monopole) 2D Helmholtz wave field, generated by a point source, towards a "perfect point drain" located at the corresponding image point. Moreover, a prototype with λ/5 super-resolution property for one microwave frequency has been manufactured and tested (Ma et al, 2010). However, software simulations or experimental measurements for a broad band of frequencies have not been reported. Here we present simulations with a non-perfect drain for a device equivalent to the MFE, called the Spherical Geodesic Waveguide (SGW), that predict up to λ/500 super-resolution close to discrete frequencies. These frequencies are directly connected with the well-known Schumann resonance frequencies of spherical symmetric systems. Out of these frequencies, the SGW does not show super-resolution in the analysis performed.

physics.optics↗

arXiv2010

Extraordinary transmission induced by defects in semitransparent screens

In this letter we present an analytical theory of Extraordinary optical transmission (EOT) through semi-transparent screens, such as thin metallic plates or high permittivity dielectric slabs. Using this theory we show that EOT appears not only for screens perforated by holes or slits, but also for screens loaded by any defects, including opaque defects. These results widen the scope of EOT concept, opening up the way to the study of new physical effects.

physics.optics↗

arXiv2003

Weak-Coupling-Like Time Evolution of Driven Four-Level Systems in the Strong-Coupling Regime

It is shown analytically that there exists a natural basis in terms of which the nonperturbative time evolution of an important class of driven four-level systems in the strong-coupling regime decouples and essentially reduces to the corresponding time evolution in the weak-field regime, exhibiting simple Rabi oscillations between the different relevant quantum states. The predictions of the model are corroborated by an exact numerical calculation.

quant-ph↗