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B. A. van Tiggelen

Publications and source records attributed to B. A. van Tiggelen.

At least 19 recordsLinked to original sources
arXiv2025

Time-Reversal Mirror inside a granular suspension: a way of measuring the ultrasound diffusion coefficient

We demonstrate that the diffusion coefficient, $D$, for ultrasound propagating in a multiple scattering medium, such as a dense granular suspension, can be measured using a time reversal experiment. This requires an unprecedented experimental setup in which a piezoelectric transducer, acting as a Time-Reversal Mirror (TRM), is embedded within the granular suspension at a depth much larger than the scattering mean free path, while an array of transducers is placed in the far field of the scattering sample. A single element of the array emits a short pulse and the TRM records the resulting ultrasonic field, which consists of a ballistic coherent wave followed by a coda wave. When the entire coda wave is time-reversed and re-emitted from the TRM, it is observed to refocus on the original source, with a focal spot size that decreases with the inverse depth of the TRM, characteristic of a diffusive regime. Time-reversal of short windows selected at different times $t$ in the coda wave reveals a focal spot size that decreases as the inverse square root of time, i.e., $1 / \sqrt{Dt}$. By fitting the predictions of a microscopic diffusion theory to our experimental data, we are able to accurately measure the diffusion coefficient in the granular suspension. Remarkably, this method does not require ensemble averaging due to stability of time-reversal against statistical fluctuations.

cond-mat.soft↗
arXiv2024

Mesoscopic Theory of Wavefront Shaping to Focus Waves inside Disordered Media

We describe the {theory of focusing waves} to a predefined spatial point {inside} a disordered {three-dimensional medium} by the external shaping of {$N$} different field sources outside the medium, {also known as wavefront shaping}. We {derive} the energy density of the wave field {both} near the focal point and anywhere else inside the medium, {averaged over realizations\textit{ after} focusing}. {To this end, we conceive of a point source at the focal point that emits waves to a detector array that - by time reversal - emits the desired shaped fields. }%endcolor {It appears that the energy} density is formally equal to intensity speckle described by {the so-called} $C_1$, $C_2$, $C_3$ and even $C_0$ {correlations} in mesoscopic transport theory, {yet the density also obeys a diffusion equation}. The $C_1$ {correlations} describes the focusing in the random medium very well, but do not generate a new source of energy that {is conceived} at the focal point. A source emerges {only} when the $C_2$ speckle is incorporated. The role of $C_0$ speckle, describing fluctuations in the {local density of optical states (LDOS)} is also investigated, {but hardly plays a role in the focusing. } Finally, we use the {concept of an energy source inside the medium} to model the {well-known} optimized transmission by a slab using wavefront shaping.

physics.optics↗
arXiv2021

Longitudinal Angular Momentum in Magneto-Mie Scattering: Quantum Vacuum Correction to the Einstein-De Haas effect

This work investigates the angular momentum of the electromagnetic quantum vacuum residing in a dielectric Mie sphere subject to the Faraday effect. Longitudinal electric modes are excited on its surface and are also created inside the sphere by the Faraday effect.The electromagnetic quantum vacuum creates a vortex of the Poynting vector that varies as $1/r$ to the center of the sphere and is associated with longitudinal angular momentum, connected to the vector potential $\mathbf{A}(\mathbf{r},t)$. It emerges as a non-negligible quantum vacuum correction to the classical (diamagnetic) Einstein-De Haas effect in which an applied external magnetic field - via its action on microscopic magnetism - enforces macroscopic rotation.

physics.atom-ph↗
arXiv2021

Longitudinal modes in diffusion and localization of light

In this work we include the elastic scattering of longitudinal electromagnetic waves in transport theory using a medium filled with point-like, electric dipoles. The interference between longitudinal and transverse waves creates two new channels among which one allows energy transport. This picture is worked out by extending the independent scattering framework of radiative transfer to include binary dipole-dipole interactions. We calculate the diffusion constant of light in the new transport channel and investigate the role of longitudinal waves in other aspects of light diffusion by considering the density of states, equipartition, and Lorentz local field. In the strongly scattering regime, the different transport mechanisms couple and impose a minimum conductivity of electromagnetic waves, thereby preventing Anderson localization of light in the medium. We extend the self-consistent theory of localization and compare the predictions to extensive numerical simulations.

cond-mat.dis-nn↗
arXiv2019

Generalized Abraham Forces on Molecules: from classical to quantum

Abraham forces are defined as electromagnetic forces on neutral objects caused by the presence of slow, time-dependent, homogeneous electromagnetic fields. Only a few experimental observations have been reported, and different formulations exist in literature. The ``standard" Abraham force is usually associated with the full derivative $\partial_t(\mathbf{E} \times \mathbf{B})$ of homogeneous electric and magnetic fields. We show that this full derivative is wrong in general, since the classical Maxwell theory contains subtle induced-dipole forces that contribute to the Abraham force, which thus breaks the dual symmetry between electric and magnetic components. We investigate other manifestations of Abraham forces and torques and estimate orders of magnitude, e.g related to chiral, moving or rotating matter. Some of them are also severely violating dual symmetry. We provide a quantum description of the Abraham force. Apart from being more elegant and less technical, this quantum treatment paves the way for future studies of Abraham forces on complex molecules involving spin and spin-orbit coupling, and also facilitates the inclusion of the quantum vacuum.

physics.optics↗
arXiv2018

Transverse confinement of ultrasound through the Anderson transition in 3D mesoglasses

We report an in-depth investigation of the Anderson localization transition for classical waves in three dimensions (3D). Experimentally, we observe clear signatures of Anderson localization by measuring the transverse confinement of transmitted ultrasound through slab-shaped mesoglass samples. We compare our experimental data with predictions of the self-consistent theory of Anderson localization for an open medium with the same geometry as our samples. This model describes the transverse confinement of classical waves as a function of the localization (correlation) length, $ξ$ ($ζ$), and is fitted to our experimental data to quantify the transverse spreading/confinement of ultrasound all of the way through the transition between diffusion and localization. Hence we are able to precisely identify the location of the mobility edges at which the Anderson transitions occur.

cond-mat.dis-nn↗
arXiv2017

Position-dependent radiative transfer as a tool for studying Anderson localization: Delay time, time-reversal and coherent backscattering

Previous work has established that the localized regime of wave transport in open media is characterized by a position-dependent diffusion coefficient. In this work we study how the concept of position-dependent diffusion affects the delay time, the transverse confinement, the coherent backscattering, and the time reversal of waves. Definitions of energy transport velocity of localized waves are proposed. We start with a phenomenological model of radiative transfer and then present a novel perturbational approach based on the self-consistent theory of localization. The latter allows us to obtain results relevant for realistic experiments in disordered quasi-1D wave guides and 3D slabs.

cond-mat.dis-nn↗
arXiv2016

Dynamic coherent backscattering of ultrasound in three-dimensional strongly-scattering media

We present measurements of the diffusion coefficient of ultrasound in strongly scattering three-dimensional (3D) disordered media using the dynamic coherent backscattering (CBS) effect. Our experiments measure the CBS of ultrasonic waves using a transducer array placed in the far-field of a 3D slab sample of brazed aluminum beads surrounded by vacuum. We extend to 3D media the general microscopic theory of CBS that was developed initially for acoustic waves in 2D. This theory is valid in the strong scattering, but still diffuse, regime that is realized in our sample, and is evaluated in the diffuse far field limit encountered in our experiments. By comparing our theory with the experimental data, we obtain an accurate measurement of the diffusion coefficient of ultrasound in our sample. We find that the value of $D$ is quite small, $0.74 \pm 0.03$ mm$^2/μ$s, and comment on the implications of this slow transport for the energy velocity.

cond-mat.dis-nn↗
arXiv2016

Photon Hall Scattering from Alkaline-earth-like atoms and Alkali-like ions

We investigate the possibility of observing a magneto-transverse scattering of photons from alkaline-earth-like atoms as well as alkali-like ions and provide orders of magnitude. The transverse magneto-scattering is physically induced by the interference between two possible quantum transitions of an outer electron in a S-state, one dispersive electric-dipole transition to a P-orbital state and a second resonant electric-quadrupole transition to a P-orbital state. In contrast with previous mechanisms proposed for such an atomic photonic Hall effect, no real photons are scattered by the electric-dipole allowed transition, which increases the ratio of Hall current to background photons significantly. The main experimental challenge is to overcome the small detection threshold, with only 10^{-5} photons scattered per atom per second.

physics.atom-ph↗
arXiv2016

Anderson mobility gap probed by dynamic coherent backscattering

We use dynamic coherent backscattering to study one of the Anderson mobility gaps in the vibrational spectrum of strongly disordered three-dimensional mesoglasses. Comparison of experimental results with the self-consistent theory of localization allows us to estimate the localization (correlation) length as a function of frequency in a wide spectral range covering bands of diffuse transport and a mobility gap delimited by two mobility edges. The results are corroborated by transmission measurements on one of our samples.

cond-mat.dis-nn↗
arXiv2013

Observation of infinite-range intensity correlations above, at and below the 3D Anderson localization transition

We investigate long-range intensity correlations on both sides of the Anderson transition of classical waves in a three-dimensional (3D) disordered material. Our ultrasonic experiments are designed to unambiguously detect a recently predicted infinite-range C0 contribution, due to local density of states fluctuations near the source. We find that these C0 correlations, in addition to C2 and C3 contributions, are significantly enhanced near mobility edges. Separate measurements of the inverse participation ratio reveal a link between C0 and the anomalous dimension Δ_2, implying that C0 may also be used to explore the critical regime of the Anderson transition.

cond-mat.dis-nn↗
arXiv2013

A single-oscillator quantum model for magnetochiral birefringence

We derive an analytical expression for the magnetochiral birefringence of a dilute diamagnetic chiral molecular medium subjet to a constant magnetic field. We use the single-oscillator model of Condon et al. [1, 2] to describe the optical properties of the individual molecules. The result is a function of the refractive index and the rotatory power. This result is compared to experimental data.

physics.chem-ph↗
arXiv2010

Transverse confinement of waves in 3D random media

We study the transmission of a tightly focused beam through a thick slab of 3D disordered medium in the Anderson localized regime. We show that the transverse profile of the transmitted beam exhibits clear signatures of Anderson localization and that its mean square width provides a direct measure of the localization length. For a short incident pulse, the width is independent of absorption.

cond-mat.dis-nn↗
arXiv2009

Localization of ultrasound in a three-dimensional elastic network

After exactly half a century of Anderson localization, the subject is more alive than ever. Direct observation of Anderson localization of electrons was always hampered by interactions and finite temperatures. Yet, many theoretical breakthroughs were made, highlighted by finite-size scaling, the self-consistent theory and the numerical solution of the Anderson tight-binding model. Theoretical understanding is based on simplified models or approximations and comparison with experiment is crucial. Despite a wealth of new experimental data, with microwaves, light, ultrasound and cold atoms, many questions remain, especially for three dimensions. Here we report the first observation of sound localization in a random three-dimensional elastic network. We study the time-dependent transmission below the mobility edge, and report ``transverse localization'' in three dimensions, which has never been observed previously with any wave. The data are well described by the self-consistent theory of localization. The transmission reveals non-Gaussian statistics, consistent with theoretical predictions.

cond-mat.dis-nn↗
arXiv2009

Phase statistics of seismic coda waves

We report the analysis of the statistics of the phase fluctuations in the coda of earthquakes recorded during a temporary experiment deployed at Pinyon Flats Observatory, California. The practical measurement of the phase is discussed and the main pitfalls are underlined. For large values, the experimental distributions of the phase first, second and third derivatives obey universal power-law decays whose exponents are remarkably well predicted by circular Gaussian statistics. For small values, these distributions are flat. The details of the transition between the plateau and the power-law behavior are governed by the wavelength. The correlation function of the first phase derivative along the array shows a simple algebro-exponential decay with the mean free path as the only length scale. Although only loose bounds are provided in this study, our work suggests a new method to estimate the degree of heterogeneity of the cr

physics.geo-ph↗
arXiv2008

Anderson localization of a Bose-Einstein condensate in a 3D random potential

We study the effect of Anderson localization on the expansion of a Bose-Einstein condensate, released from a harmonic trap, in a 3D random potential. We use scaling arguments and the self-consistent theory of localization to show that the long-time behavior of the condensate density is controlled by a single parameter equal to the ratio of the mobility edge and the chemical potential of the condensate. We find that the two critical exponents of the localization transition determine the evolution of the condensate density in time and space.

cond-mat.dis-nn↗