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Marcel Filoche

Publications and source records attributed to Marcel Filoche.

At least 19 recordsLinked to original sources
arXiv2026

Wave Transport in Fourier Quasicrystals Revealed by Water Waves

Fourier quasicrystals are aperiodic structures whose diffraction spectrum consists not of a dense set of Bragg peaks, as in ordinary quasicrystals, but of isolated ones scattered across a discrete, nonperiodic set. This sparse reciprocal-space structure should leave wave transport largely undisturbed except at a few selected wavevectors. We put this prediction to the test using surface water waves scattering off a two-dimensional Fourier quasicrystal. Full-field measurements reveal three distinct transport regimes as the incident wavevector increases: transparency, selective scattering, and strong scattering. By reconstructing the structure factor from the measured wavefields, we directly relate these regimes to the underlying reciprocal-space structure. Our results establish Fourier quasicrystals as a physical platform in which wave transport can be controlled through the organization of diffraction peaks in reciprocal space.

cond-mat.soft↗
arXiv2026

Efficient Analysis of Carrier Transport and TM-TE Emission in AlGaN UVC LEDs via Multi-band Localization Landscape Theory

AlGaN-based UVC LEDs (220-250 nm) suffer from poor hole confinement and strain-induced |Z>-band dominance at high Al content (>60%), leading to increased TM emission and reduced external quantum efficiency (EQE). While conventional k.p models combined with Schrodinger, Poisson, and drift-diffusion solvers are widely used to study optical transitions, they are computationally expensive. In this work, we apply the multiband Localization Landscape (LL) model, including the effect of strain, as an alternative that replaces the eigenvalue problem to efficiently capture quantum effects and carrier localization. Using the 3D multi-band LL model with the Wigner-Weyl formalism, we reproduce emission and absorption spectra trends similar to the results in 3D k.p calculations, but with significantly reduced simulation time. The polarization ratio also agrees well with published experimental results across a wide spectral range. Furthermore, we analyze electrical characteristics such as band structure, polarization switching, and carrier confinement under alloy fluctuations and strain. This multi-band LL-based approach provides a fast and reliable solution for understanding and optimizing UVC LED performance.

physics.app-ph↗
arXiv2026

Experimentally controlling scattering of water waves in correlated disorder

Wave propagation in complex media is a universal problem spanning optics, acoustics, mechanics, and condensed matter physics. While disorder usually causes strong scattering, recent theory predicts that a special class of correlated disorder, known as stealthy hyperuniformity, can suppress scattering at long wavelengths, making a material transparent despite remaining structurally disordered and far from a simple homogenization regime. Experimental evidence of this remarkable transport regime within a medium has, however, remained limited. Here we report a direct, spatially resolved experimental observation of a transition between scattering and non-scattering wave transport induced by hyperuniform correlations. Using water waves as a model platform, we image both the amplitude and phase of the wavefield as it propagates through a two-dimensional disordered structure. This enables us to extract quantitative transport observables, including extinction lengths, statistical fluctuations, and energy-flow patterns, and to directly identify the boundary of the hyperuniform transparency regime. Our results provide a quantitative experimental validation of the transport regimes predicted for stealthy hyperuniform disorder and demonstrate that correlated disorder offers a powerful and practical route to control wave propagation in realistic systems across wave physics.

cond-mat.soft↗
arXiv2025

Localization-landscape generalized Mott-Berezinski\u{i} formula

We introduce a conceptual reformulation of the Mott-Berezinski\u{i} (MB) theory of low-frequency AC conductivity in disordered systems based on localization landscape theory. Instead of assuming uniform localization and fixed hopping distances, transport is described through an effective potential whose geometry encodes the spatial organization and energy-dependent localization of quantum states. Using the associated Agmon metric, we define a generalized Mott scale that replaces the classical hopping length with a geometric criterion set by the disorder landscape. This framework naturally incorporates strong spatial inhomogeneity and yields the AC conductivity directly from the effective potential. The standard MB result is recovered as a limiting case. Our approach extends the conceptual foundation of MB theory to arbitrary disordered media and energies approaching the mobility edge, providing a unified description of AC transport in complex quantum materials.

cond-mat.dis-nn↗
arXiv2025

From percolation transition to Anderson localization in one-dimensional speckle potentials

Classical particles in random potentials typically experience a percolation phase transition, being trapped in clusters of mean size $\chi$ that diverges algebraically at a percolation threshold. In contrast, quantum transport in random potentials is controlled by the Anderson localization length, which shows no distinct feature at this classical critical point. Here, we present a comprehensive theoretical analysis of the semi-classical crossover between these two regimes by studying particle propagation in a one-dimensional, red speckle potential, which hosts a percolation transition at its upper bound. As the system deviates from the classical limit, we find that the algebraic divergence of $\chi$ continuously connects to a smooth yet non-analytic increase of the localization length. We characterize this behavior both numerically and theoretically using a semi-classical approach. In this crossover regime, the correlated and non-Gaussian nature of the speckle potential becomes essential, causing the standard Dorokhov-Mello-Pereyra-Kumar (DPMK) description for uncorrelated disorder to break down. Instead, we predict the emergence of a bimodal transmission distribution, a behavior normally absent in one dimension, which we capture within our semi-classical analysis. Deep in the quantum regime, the DMPK framework is recovered and the universal features of Anderson localization reappear.

cond-mat.dis-nn↗
arXiv2025

Localization structure of electronic states in the quantum Hall effect

We investigate the localization of electronic states in the integer quantum Hall effect using a magnetic localization landscape (MLL) approach. By studying a continuum Schr\"odinger model with disordered electrostatic potential, we demonstrate that the MLL, defined via a modified landscape function incorporating magnetic effects, captures key features of quantum state localization. The MLL effective potential reveals the spatial confinement regions and provides predictions of eigenstate energies, particularly in regimes where traditional semiclassical approximations break down. Numerical simulations show that below a critical energy, states localize around minima of the effective potential, while above it, they cluster around maxima-with edge effects becoming significant near boundaries. Bridging the gap between semiclassical intuition and full quantum models, the MLL offers a robust framework to understand transport and localization in disordered quantum Hall systems, and extends the applicability of landscape theory to magnetic systems.

cond-mat.mes-hall↗
arXiv2025

Robin Green Function Estimates and a Model of Mammalian Lungs

The present paper establishes delicate properties of the Green function with Robin boundary conditions, in particular, elucidating the nature of the passage between the Dirichlet-like and Neumann-like behavior. This yields sharp quantifiable bounds on the corresponding harmonic measure and proves the phase transition in the behavior of the total flow earlier conjectured in physics literature in concert with the efficacy of mammalian lungs.

math.AP↗
arXiv2025

Theoretical predictions for ultrasensitive sensing in three-dimensional stochastic interferometry

We show that a random light field can be harnessed for high-precision metrology by introducing specific boundary conditions in the form of Lambertian reflections inside a cavity. We demonstrate a quantifiable and reproducible interferometric response to minute perturbations in wavelength, refractive index, and geometry, predicting high sensitivities consistent with experimental measurements of geometrical deformations down to the picometer scale.

physics.optics↗
arXiv2023

Anderson mobility edge as a percolation transition

The location of the mobility edge is a long standing problem in Anderson localization. In this paper, we show that the effective confining potential introduced in the localization landscape (LL) theory predicts the onset of delocalization in 3D tight-binding models, in a large part of the energy-disorder diagram. Near the edge of the spectrum, the eigenstates are confined inside the basins of the LL-based potential. The delocalization transition corresponds to the progressive merging of these basins resulting in the percolation of this classically-allowed region throughout the system. This approach, shown to be valid both in the cases of uniform and binary disorders despite their very different phase diagrams, allows us to reinterpret the Anderson transition in the tight-binding model: the mobility edge appears to be composed of two parts, one being understood as a percolation transition.

cond-mat.dis-nn↗
arXiv2023

Realization-dependent model of hopping transport in disordered media

At low injection or low temperatures, electron transport in disordered semiconductors is dominated by phonon-assisted hopping between localized states. A very popular approach to this hopping transport is the Miller-Abrahams model that requires a set of empirical parameters to define the hopping rates and the preferential paths between the states. We present here a transport model based on the localization landscape (LL) theory in which the location of the localized states, their energies, and the coupling between them are computed for any specific realization, accounting for its particular geometry and structure. This model unveils the transport network followed by the charge carriers that essentially consists in the geodesics of a metric deduced from the LL. The hopping rates and mobility are computed on a paradigmatic example of disordered semiconductor, and compared with the prediction from the actual solution of the Schr\"odinger equation. We explore the temperature-dependency for various disorder strengths and demonstrate the applicability of the LL theory in efficiently modeling hopping transport in disordered systems.

cond-mat.dis-nn↗
arXiv2022

The electronic disorder landscape of mixed halide perovskites

Bandgap tunability of lead mixed-halide perovskites makes them promising candidates for various applications in optoelectronics since they exhibit sharp optical absorption onsets despite the presence of disorder from halide alloying. Here we use localization landscape theory to reveal that the static disorder due to compositional alloying for iodide:bromide perovskite contributes at most 3 meV to the Urbach energy. Our modelling reveals that the reason for this small contribution is due to the small effective masses in perovskites, resulting in a natural length scale of around 20nm for the "effective confining potential" for electrons and holes, with short range potential fluctuations smoothed out. The increase in Urbach energy across the compositional range agrees well with our optical absorption measurements. We model systems of sizes up to 80 nm in three dimensions, allowing us to explore halide segregation, accurately reproducing the experimentally observed absorption spectra and demonstrating the scope of our method to model electronic structures on large length scales. Our results suggest that we should look beyond static contribution and focus on the dynamic temperature dependent contribution to the Urbach energy.

cond-mat.mtrl-sci↗
arXiv2022

Low and high-energy localization landscapes for tight-binding Hamiltonians in 2D lattices

Localization of electronic wave functions in modern two-dimensional (2D) materials such as graphene can impact drastically their transport and magnetic properties. The recent localization landscape (LL) theory has brought many tools and theoretical results to understand such localization phenomena in the continuous setting, but with very few extensions so far to the discrete realm or to tight-binding Hamiltonians. In this paper, we show how this approach can be extended to almost all known 2D~lattices, and propose a systematic way of designing LL even for higher dimension. We demonstrate in detail how this LL theory works and predicts accurately not only the location, but also the energies of localized eigenfunctions in the low and high energy regimes for the honeycomb and hexagonal lattices, making it a highly promising tool for investigating the role of disorder in these materials.

cond-mat.dis-nn↗
arXiv2022

Localization landscape for interacting Bose gases in one-dimensional speckle potentials

While the properties and the shape of the ground state of a gas of ultracold bosons are well understood in harmonic potentials, they remain for a large part unknown in the case of random potentials. Here, we use the localization-landscape (LL) theory to study the properties of the solutions to the Gross-Pitaevskii equation (GPE) in one-dimensional (1D) speckle potentials. In the cases of attractive interactions, we find that the LL allows one to predict the position of the localization center of the ground state (GS) of the GPE. For weakly repulsive interactions, we point out that the GS of the quasi-1D GPE can be understood as a superposition of a finite number of single-particle states, which can be computed by exploiting the LL. For intermediate repulsive interactions, we introduce a Thomas-Fermi-like approach for the GS which holds in the smoothing regime, well beyond the usual approximation involving the original potential. Moreover, we show that, in the Lifshitz glass regime, the particle density and the chemical potential can be well estimated by the LL. Our approach can be applied to any positive-valued random potential endowed with finite-range correlations and can be generalized to higher-dimensional systems.

cond-mat.quant-gas↗
arXiv2021

Wigner-Weyl description of light absorption in disordered semiconductor alloys using the localization landscape theory

The presence of disorder in semiconductors can dramatically change their physical properties. Yet, models faithfully accounting for it are still scarce and computationally inefficient. We present a mathematical and computational model able to simulate the optoelectronic response of semiconductor alloys of several tens of nanometer sidelength, while at the same time accounting for the quantum localization effects induced by the compositional disorder at the nano-scale. The model is based on a Wigner-Weyl analysis of the structure of electron and hole eigenstates in phase space made possible by the localization landscape theory. After validation against eigenstates-based computations in 1D and 2D, our model is applied to the computation of light absorption in 3D InGaN alloys of different compositions. We obtain the detailed structures of the absorption tail below the average bandgap and the Urbach energies of all simulated compositions. Moreover, the Wigner-Weyl formalism allows us to define and compute 3D maps of the effective locally absorbed power at all frequencies. Finally the proposed approach opens the way to generalize this method to all energy-exchange processes such as radiative and non-radiative recombination in realistic devices.

cond-mat.dis-nn↗
arXiv2021

Spectral functions and localization landscape theory in speckle potentials

Spectral function is a key tool for understanding the behavior of Bose-Einstein condensates of cold atoms in random potentials generated by a laser speckle. In this paper we introduce a new method for computing the spectral functions in disordered potentials. Using a combination of the Wigner-Weyl approach with the landscape theory, we build an approximation for the Wigner distributions of the eigenstates in the phase space and show its accuracy in all regimes, from the deep quantum regime to the intermediate and semiclassical. Based on this approximation, we devise a method to compute the spectral functions using only the landscape-based effective potential. The paper demonstrates the efficiency of the proposed approach for disordered potentials with various statistical properties without requiring any adjustable parameters.

quant-ph↗
arXiv2021

3D stochastic interferometer detects picometer deformations and minute dielectric fluctuations of its optical volume

Optical interferometry has proven extremely powerful to investigate some of the most fundamental laws of physics, using light with very precisely controlled geometry. In the past few decades, various speckle metrology methods have emerged to harness the interferometric properties of strongly disordered light instead, using time-domain analysis of speckle patterns at a maximum rate limited by the frequency of image acquisition. The present work is based on using a centimeter-sized quartz-powder cavity with an arbitrary shape that is engineered with very high Lambertian reflectivity. When filled with a coherent monochromatic photon gas, a statistically isotropic and homogeneous 3D speckle interference pattern is obtained. A single-mode fiber is then used in combination with photon number autocorrelation analysis to detect minute changes of the speckle decorrelation spectrum, caused either by cavity deformations or fluctuations of the dielectric tensor field inside. The decorrelation spectrum is acquired over 8 to 10 frequency decades below 100 MHz, with a sensitivity that is only limited by the intrinsic photon statistics and the extrinsic instrumental noises. With typically 1700 reflections and an average photon transit path length of 62m, our 3D stochastic interferometer yields a typical finesse of 10500, and cavity deformations are detected in an ergodic fashion over a six-decade dynamic range with a power noise floor of 4x{10}^{-3} pm^2 which corresponds to 2.7 pm at 1 kHz. The cavity also operates as a speckle fluctuation amplifier that reveals decorrelation spectra due to picometric thermal motions of colloids in both single and multiple scattering regimes with a typical 100-fold sensitivity gain compared to conventional light scattering techniques.

physics.optics↗
arXiv2021

The landscape law for tight binding Hamiltonians

The present paper extends the landscape theory pioneered in [FM, ADFJM2, DFM] to the tight-binding Schr\"odinger operator on $\Z^d$. In particular, we establish upper and lower bounds for the integrated density of states in terms of the counting function based upon the localization landscape.

math-ph↗