arXiv subjects

A. A. Fernández-Marín

Publications and source records attributed to A. A. Fernández-Marín.

4 recordsLinked to original sources

arXiv2020

Delay time of waves performing Lévy walks in 1D random media

The time that waves spend inside 1D random media with the possibility of performing Lévy walks is experimentally and theoretically studied. The dynamics of quantum and classical wave diffusion has been investigated in canonical disordered systems via the delay time. We show that a wide class of disorder--Lévy disorder--leads to strong random fluctuations of the delay time; nevertheless, some statistical properties such as the tail of the distribution and the average of the delay time are insensitive to Lévy walks. Our results reveal a universal character of wave propagation that goes beyond standard Brownian wave-diffusion.

cond-mat.dis-nn↗

arXiv2016

Cross section versus time delay and trapping probability

We study the behavior of the $s$-wave partial cross section $σ(k)$, the Wigner-Smith time delay $τ(k)$, and the trapping probability $P(k)$ as function of the wave number $k$. The $s$-wave central square well is used for concreteness, simplicity, and to elucidate the controversy whether it shows true resonances. It is shown that, except for very sharp structures, the resonance part of the cross section, the trapping probability, and the time delay, reach their local maxima at different values of $k$. We show numerically that $τ(k)>0$ at its local maxima, occuring just before the resonant part of the cross section reaches its local maxima. These results are discussed in the light of the standard definition of resonance.

quant-ph↗

arXiv2015

Delay times in chaotic quantum systems

By an inductive reasoning, and based on recent results of the joint moments of proper delay times of open chaotic systems for ideal coupling to leads, we obtain a general expression for the distribution of the partial delay times for an arbitrary number of channels and any symmetry. This distribution was not completely known for all symmetry classes. Our theoretical distribution is verified by random matrix theory simulations of ballistic chaotic cavities.

cond-mat.mes-hall↗

arXiv2014

Beyond Anderson Localization in 1D: Anomalous Localization of Microwaves in Random Waveguides

Experimental evidence demonstrating that anomalous localization of waves can be induced in a controllable manner is reported. A microwave waveguide with dielectric slabs randomly placed is used to confirm the presence of anomalous localization. If the random spacing between slabs follows a distribution with a power-law tail (Lévy-type distribution), unconventional properties in the microwave-transmission fluctuations take place revealing the presence of anomalous localization. We study both theoretically and experimentally the complete distribution of the transmission through random waveguides characterized by $α=1/2$ ("Lévy waveguides") and $α=3/4$, $α$ being the exponent of the power-law tail of the Lévy-type distribution. As we show, the transmission distributions are determined by only two parameters, both of them experimentally accessible. Effects of anomalous localization on the transmission are compared with those from the standard Anderson localization.

cond-mat.dis-nn↗