55 research outputs found

    Non-analyticity in the distribution of conductances in quasi one dimensional wires

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    We show that the distribution P(g) of conductances g of a quasi one dimensional wire has non-analytic behavior in the insulating region, leading to a discontinuous derivative in the distribution near g=1. We give analytic expressions for the full distribution and extract an approximate scaling behavior valid for different strengths of disorder close to g=1.Comment: 7 pages, 3 figures. Submitted to Europhysics Letter

    Statistical analysis of the transmission based on the DMPK equation: An application to Pb nano-contacts

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    The density of the transmission eigenvalues of Pb nano-contacts has been estimated recently in mechanically controllable break-junction experiments. Motivated by these experimental analyses, here we study the evolution of the density of the transmission eigenvalues with the disorder strength and the number of channels supported by the ballistic constriction of a quantum point contact in the framework of the Dorokhov-Mello-Pereyra-Kumar equation. We find that the transmission density evolves rapidly into the density in the diffusive metallic regime as the number of channels NcN_c of the constriction increase. Therefore, the transmission density distribution for a few NcN_c channels comes close to the known bimodal density distribution in the metallic limit. This is in agreement with the experimental statistical-studies in Pb nano-contacts. For the two analyzed cases, we show that the experimental densities are seen to be well described by the corresponding theoretical results.Comment: 6 pages, 6 figure

    A Lloyd-model generalization: Conductance fluctuations in one-dimensional disordered systems

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    We perform a detailed numerical study of the conductance GG through one-dimensional (1D) tight-binding wires with on-site disorder. The random configurations of the on-site energies ϵ\epsilon of the tight-binding Hamiltonian are characterized by long-tailed distributions: For large ϵ\epsilon, P(ϵ)1/ϵ1+αP(\epsilon)\sim 1/\epsilon^{1+\alpha} with α(0,2)\alpha\in(0,2). Our model serves as a generalization of 1D Lloyd's model, which corresponds to α=1\alpha=1. First, we verify that the ensemble average lnG\left\langle -\ln G\right\rangle is proportional to the length of the wire LL for all values of α\alpha, providing the localization length ξ\xi from lnG=2L/ξ\left\langle-\ln G\right\rangle=2L/\xi. Then, we show that the probability distribution function P(G)P(G) is fully determined by the exponent α\alpha and lnG\left\langle-\ln G\right\rangle. In contrast to 1D wires with standard white-noise disorder, our wire model exhibits bimodal distributions of the conductance with peaks at G=0G=0 and 11. In addition, we show that P(lnG)P(\ln G) is proportional to GβG^\beta, for G0G\to 0, with βα/2\beta\le\alpha/2, in agreement to previous studies.Comment: 5 pages, 5 figure

    Photonic heterostructures with Levy-type disorder: statistics of coherent transmission

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    We study the electromagnetic transmission TT through one-dimensional (1D) photonic heterostructures whose random layer thicknesses follow a long-tailed distribution --L\'evy-type distribution. Based on recent predictions made for 1D coherent transport with L\'evy-type disorder, we show numerically that for a system of length LL (i) the average Lα \propto L^\alpha for 0L0 \propto L for 1α<21\le\alpha<2, α\alpha being the exponent of the power-law decay of the layer-thickness probability distribution; and (ii) the transmission distribution P(T)P(T) is independent of the angle of incidence and frequency of the electromagnetic wave, but it is fully determined by the values of α\alpha and .Comment: 4 pages, 4 figure

    Conductance of 1D quantum wires with anomalous electron-wavefunction localization

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    We study the statistics of the conductance gg through one-dimensional disordered systems where electron wavefunctions decay spatially as ψexp(λrα)|\psi| \sim \exp (-\lambda r^{\alpha}) for 0<α<10 <\alpha <1, λ\lambda being a constant. In contrast to the conventional Anderson localization where ψexp(λr)|\psi| \sim \exp (-\lambda r) and the conductance statistics is determined by a single parameter: the mean free path, here we show that when the wave function is anomalously localized (α<1\alpha <1) the full statistics of the conductance is determined by the average and the power α\alpha. Our theoretical predictions are verified numerically by using a random hopping tight-binding model at zero energy, where due to the presence of chiral symmetry in the lattice there exists anomalous localization; this case corresponds to the particular value α=1/2\alpha =1/2. To test our theory for other values of α\alpha, we introduce a statistical model for the random hopping in the tight binding Hamiltonian.Comment: 6 pages, 8 figures. Few changes in the presentation and references updated. Published in PRB, Phys. Rev. B 85, 235450 (2012

    Statistics of Impedance, Local Density of States, and Reflection in Quantum Chaotic Systems with Absorption

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    We are interested in finding the joint distribution function of the real and imaginary parts of the local Green function for a system with chaotic internal wave scattering and a uniform energy loss (absorption). For a microwave cavity attached to a single-mode antenna the same quantity has a meaning of the complex cavity impedance. Using the random matrix approach, we relate its statistics to that of the reflection coefficient and scattering phase and provide exact distributions for systems with beta=2 and beta=4 symmetry class. In the case of beta=1 we provide an interpolation formula which incorporates all known limiting cases and fits excellently available experimental data as well as diverse numeric tests.Comment: 4 pages, 1 figur

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

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    [EN] 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.A. A. F.-M. thanks the hospitality of the Laboratoire d'Acoustique de l'Universite du Mans, France, where part of this work was done. J. A. M.-B, gratefully acknowledges to Departamento de Matematica Aplicada e Estatistica, Instituto de Ciencias Matematicas e de Computacao, Universidade de Sao Paulo during which this work was completed. J.A.M.-B. was supported by FAPESP (Grant No. 2019/06931-2), Brazil. A. A. F.-M. thanks partial support by RFI Le Mans Acoustique and by the project HYPERMETA funded under the program Etoiles Montantes of the Region Pays de la Loire. V. A. G. acknowledges support by MCIU (Spain) under the Project number PGC2018-094684-B-C22.Razo-López, LA.; Fernández-Marín, AA.; Mendez-Bermudez, JA.; Sánchez-Dehesa Moreno-Cid, J.; Gopar, VA. (2020). Delay time of waves performing Levy walks in 1D random media. Scientific Reports. 10(1):1-8. https://doi.org/10.1038/s41598-020-77861-xS18101Wigner, E. P. Lower limit for the energy derivative of the scattering phase shift. Phys. Rev. 147, 145–147 (1955).Smith, F. T. Lifetime matrix in collision theory. Phys. Rev. 119, 2098–2098 (1960).Fercher, A. F., Drexler, W., Hitzenberger, C. K. & Lasser, T. Optical coherence tomography -principles and applications. Rep. Prog. Phys. 66, 239–303 (2003).Lubatsch, A. & Frank, R. 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    Universality of the Wigner time delay distribution for one-dimensional random potentials

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    We show that the distribution of the time delay for one-dimensional random potentials is universal in the high energy or weak disorder limit. Our analytical results are in excellent agreement with extensive numerical simulations carried out on samples whose sizes are large compared to the localisation length (localised regime). The case of small samples is also discussed (ballistic regime). We provide a physical argument which explains in a quantitative way the origin of the exponential divergence of the moments. The occurence of a log-normal tail for finite size systems is analysed. Finally, we present exact results in the low energy limit which clearly show a departure from the universal behaviour.Comment: 4 pages, 3 PostScript figure

    Statistics of Dynamics of Localized Waves

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    The measured distribution of the single-channel delay time of localized microwave radiation and its correlation with intensity differ sharply from the behavior of diffusive waves. The delay time is found to increase with intensity, while its variance is inversely proportional to the fourth root of the intensity. The distribution of the delay time weighted by the intensity is found to be a double-sided stretched exponential to the 1/3 power centered at zero. The correlation between dwell time and intensity provides a dynamical test of photon localization.Comment: submitted to PRL; 4 pages including 6 figure
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