In the context of the energy transition and the growing demand for electrochemical energy storage, the development of efficient and sustainable battery materials is a major scientific and technological challenge. Chalcogenide-based materials, including sulfides, selenides, and tellurides, have attracted increasing attention due to their versatile structural and electronic properties. This article provides a concise overview of the role of chalcogenides in battery technologies, from their historical contribution to the emergence of lithium-ion batteries to their current applications as intercalation and conversion electrodes, nanostructured negative electrodes, solid electrolytes, and lithium-rich positive electrodes in solid-state batteries. Particular emphasis is placed on the relationships between composition, structure, electrochemical mechanisms, and performance. Finally, the potential of chalcogenide materials for post-lithium battery technologies, such as sodium-, potassium-, and magnesium-ion systems, is discussed, highlighting remaining challenges and future research perspectives.
Cet article de revue présente les résultats récents concernant la description des gaz de bosons unidimensionnels avec interactions de contact répulsives par une approche hydrodynamique généralisée. Les résultats obtenus par les auteurs sont plus particulièrement mis en avant.
A theoretical result based on nonlinear quantum electrodynamics could suggest the invariance of the fine-structure constant everywhere in the Universe and at any epochs of its history. The present paper updates while summarizing this theoretical framework, and provides a critical survey of recent astrophysical observations related to this constant’s value. We conclude that, from an observational point of view, this constant could indeed be invariant over cosmic space and epochs, in line with the theoretical study.
Nous montrons que la théorie de champ moyen minimale à utiliser pour le calcul des fonctions de distribution de paires g σ σ ′ ( r , r ′ ) d’un gaz superfluide de fermions de spin 1/2 spatialement homogène non polarisé n’est pas la théorie BCS statique ordinaire, mais la théorie BCS dépendant du temps linéarisée, mise en œuvre par le truchement du théorème de fluctuation-dissipation. En effet, la première ignore totalement la branche d’excitation acoustique — les phonons — du superfluide, alors que la seconde en tient compte explicitement, ainsi que des fluctuations quantiques induites par le continuum de paires brisées. Contrairement à la première, la seconde théorie (i) répercute l’effet de ces excitations collectives sur l’équation d’état du système, y compris à température nulle, (ii) permet à la fonction g ↑ ↓ ( r , r ′ ) de descendre à distance assez grande strictement en dessous de sa valeur asymptotique ( ρ / 2 ) 2 où ρ est la densité du gaz, comme il se doit d’après l’hydrodynamique quantique de Landau et Khalatnikov à basse température, et (iii) prédit dans la fonction g ↑ ↑ ( r , r ′ ) à courte distance des contributions sous-dominantes en | r - r ′ | 2 ln | r - r ′ | à 3D et en | r - r ′ | 2 ln - ln | r - r ′ | à 2D, à côté des contributions dominantes en | r - r ′ | à 3D et en | r - r ′ | 2 ln | r - r ′ | à 2D déjà présentes dans la théorie BCS statique mais avec un coefficient plus faible. Cette discussion est pertinente pour les travaux théoriques récents d’Obeso-Jureidini et de Romero-Rochín, et pour les expériences en cours sur les gaz d’atomes froids à l’ENS et au MIT.
The Madelung equations express the Schr & ouml;dinger equation as a continuity equation and modified Hamilton-Jacobi equation. These equations are equivalent to the Euler equations for a compressible, potential flow, when classical pressure per unit density is replaced by the quantum potential per unit mass. We extend this hydrodynamic interpretation by quantising a single, spinless, non-relativistic particle constrained to a surface wave with small slope. The wave is distinct from the wave function and, in order to reproduce the Schr & ouml;dinger equation, it must satisfy the kinematic boundary condition for a free surface advected by twice the Madelung velocity field.
We use the configuration-space Faddeev formalism to study scattering of three particles in the double continuum where all particles are free. All scattering processes, starting from and ending in both single and double continua, are collected in a unique matrix. We apply our method to the benchmark system of neutron-deuteron scattering.
The present article concerns the stochastic modeling of the turbulent dissipation field and in particular its temporal evolution. To do so, we will be calling for a random distribution, ubiquitous in several aspects of physics and probability theory, known as the Gaussian Multiplicative Chaos (GMC), that takes its roots in the phenomenology of fluid turbulence. Firstly introduced by Mandelbrot, shortly after Yaglom's discrete multiplicative cascade models, and rigorously studied by Kahane, the GMC appears as an appropriate statistically homogeneous model of the turbulent dissipation field. In this article, we will be recalling several ingredients of the associated turbulent phenomenology and its stochastic representation as a GMC, and propose a generalization to a spatio-temporal framework. All along the presentation of known properties in space, and in order to support new propositions concerning the temporal evolution, we will be calling for a comparison against Direct Numerical Simulations of the Navier-Stokes equations extracted from a publicly accessible database.
Collective motion of micro-swimmers leads to the emergence of coherent macroscopic structures. In the case of diluted cultures of micro-organisms, a typical dotted pattern can spontaneously appear within a few minutes, even in the absence of external stimulus, a signature of bioconvection. However, we know little about the resilience of bioconvective plumes facing an environmental alteration. Here, we take advantage of the phototactic behaviour of the green micro-algae Chlamydomonas reinhardtii to perturb bioconvection with an asymmetric lightning. Our experiments demonstrate that plumes first disappear, leaving place for a new anisotropic structure at the illuminated wall. We characterise the dynamics of this rising pattern at various scales and propose a mechanism based on the physical properties of the micro-swimmers.
We challenge the standard picture of decohering Schr & ouml;dinger cat states as an ensemble average obeying a Lindblad master equation, brought about locally from an irreversible interaction with an environment. We generate self-consistent collections of pure system states correlated with specific environmental records, corresponding to the function of the wave-particle correlator first introduced in Carmichael et al. [Phys. Rev. Lett. 85 (2000)]. In the spirit of Carmichael et al. [in Coherent States: Past, Present and Future, World Scientific, 1994], we find that the complementary unravelings evince a pronounced disparity when the "position" and "momentum" of the damped cavity mode an explicitly open quantum system are measured. Intensity-field correlations may largely deviate from a monotonic decay, while Wigner functions of the cavity state display contrasting manifestations of quantum interference when conditioned on photon counts sampling a continuous photocurrent. In turn, the conditional photodetection events mark the contextual diffusion of both the net charge generated at the homodyne detector, and the electromagnetic field amplitude in the resonator.
I provide a simple argument that the experimental observation of gravitationally induced entanglement rules out the validity of current gravitational collapse models. This is consistent with the recent claim to the contrary in [Trillo and Navascu & eacute;s, Phys. Rev. D, 111, (2025)], if one takes into account the physical constraints of actual table-top gravity experiments.
We show that the minimal mean-field theory to use for calculating the pair distribution functions g_σσ'(r⃗,r⃗ ') of a spatially homogeneous, unpolarized spin-1/2 superfluid Fermi gas is not the ordinary static BCS theory, but the linearized time-dependent BCS theory implemented via the fluctuation-dissipation theorem. Indeed, the former completely ignores the acoustic excitation branch - the phonons - of the superfluid, while the latter explicitly takes it into account, as well as the quantum fluctuations induced by the broken-pair continuum. Unlike the first, the second theory (i) reflects the effect of these collective excitations on the system's equation of state, including at zero temperature, (ii) allows the function g_↑↓(r⃗,r⃗ ') to go at sufficiently large distances strictly below its asymptotic value (ρ/2)^2 where ρ is the gas density, as expected according to the quantum hydrodynamics of Landau and Khalatnikov at low temperatures, and (iii) predicts in the function g_↑↑(r⃗,r⃗ ') at short distances subdominant contributions |r⃗-r⃗ '|^2ln|r⃗-r⃗ '| in 3D and |r⃗-r⃗ '|^2ln(-ln|r⃗-r⃗ '|) in 2D, alongside the dominant contributions |r⃗-r⃗ '| in 3D and |r⃗-r⃗ '|^2ln|r⃗-r⃗ '| in 2D already present in static BCS theory but with a lower coefficient. This discussion is relevant to the recent theoretical work of Obeso-Jureidini and Romero-Rochin, and to the ongoing experiments on cold atomic gases at ENS and MIT.
The Hawking effect amplifies fluctuations in the vicinity of horizons, both in black holes and in analogue platforms. Here, we consider a polariton simulator and numerically examine the stimulated Hawking effect using a coherent probe incident on the horizon from the exterior. We implement an experimentally realistic effective spacetime that supports a quasinormal mode (QNM) in the vicinity of the horizon. We find that the stimulated Hawking effect manifests as transmission into a negative-energy Bogoliubov channel inside the horizon, consistent with pseudo-unitary Bogoliubov scattering. Moreover, transmission across the horizon peaks at the QNM frequency. The computed spectral signatures provide a practical guide for future experimental investigations of the Hawking effect and its interplay with QNMs, an open question in quantum field theory in curved spacetime.
The recent development of single-atom-resolved probes has made full counting statistics measurements accessible in quantum gas experiments. This capability provides access to high-order moments of physical observables, from which cumulants, or equivalently connected correlations, can be precisely determined. Through a selection of recent cold atom experiments, this article illustrates the significance of connected correlations in characterizing ensembles of interacting quantum particles. First, non-zero connected correlations of order n >2 unambiguously identify non-Gaussian quantum states. Second, connected correlations of order n identify clusters made of n elements whose statistical properties are irreducible to combinations of smaller clusters. The ability to identify such multi-particle clusters offers an interesting perspective on strongly correlated quantum states of matter at the microscopic scale.
Quantum technologies with quantum correlated light require photodiodes with near-perfect 'true' quantum efficiency, the definition of which adequately accounts for the photodiode dark noise. Future squeezed-light-enhanced gravitational wave detectors could in principle achieve higher sensitivities with a longer laser wavelength around 2 & micro;m. Photodiodes made of extended InGaAs are available for this range, but the true quantum efficiency at room temperature and the low frequency band of gravitational waves is strongly reduced by dark noise. Here we characterize the change in performance of a commercial extended-InGaAs photodiode versus temperature. While the dark noise decreases as expected with decreasing temperature, the detection efficiency unfortunately also decreases monotonically. Our results indicate the need for a dedicated new design of photodiodes for gravitational wave detectors using 2-& micro;m laser light.
We report a two-stage, heterodyne rf-to-microwave transducer that combines a tunable electrostatic pre-amplifier with a superconducting electromechanical cavity. A metalized Si3N4 membrane (3 MHz frequency) forms the movable plate of a vacuum-gap capacitor in a microwave LC resonator. A dc bias across the gap converts any small rf signal into a resonant electrostatic force proportional to the bias, providing a voltage-controlled gain that multiplies the cavity's intrinsic electromechanical gain. In a flip-chip device with a 1.5 & micro;m gap operated at 10 mK we observe dc-tunable anti-spring shifts, and rf-to-microwave transduction at 49 V bias, achieving a charge sensitivity of 87 & micro;e/ root Hz (0.9 nV/ root Hz). Extrapolation to sub-micron gaps and state-of-the-art Q > 10(8) membrane resonators predicts sub-200 fV/ root Hz sensitivity, establishing dc-biased electromechanics as a practical route towards quantum-grade rf electrometers and low-noise modular heterodyne links for superconducting microwave circuits and charge or voltage sensing.
We perform a theoretical study of a continuous superradiant laser supporting its experimental realization at FEMTO-ST using two sequentially-emitting ensembles of ^171Yb atoms coupled to the same Fabry-Perot cavity. Using an open quantum system approach, we identify for the simplest case the parameter space where the laser reaches tens of picowatts of power with a sub-millihertz linewidth. Studying the impact of inhomogeneous frequency broadening and variations in atom-cavity coupling on the superradiant emission, we find the laser properties robust with respect to such perturbations, also thanks to the occurrence of synchronization of the atomic dipoles. We then consider a two-site configuration, in which atoms in each site are equally coupled to the cavity and have equal detunings, with different values for the two ensembles. We find for balanced and imbalanced atom numbers that synchronization leads in a certain parameter space to a single narrow spectral line whose central frequency follows the weighted average frequency. This result indicates that sequential loading can enable continuous superradiant emission for metrological applications, provided that the relative frequencies of the two ensembles are controlled to the level required by the target stability.
We clarify the origin of what is sometimes called the "topological anomalous Hall effect," provide analytical formulas to compute all the contributions to the Hall conductivity in the presence of Kondo-coupled spins and spin orbit coupling. The derivation is technical but we emphasize that the results can be very easily applied.
Based on a remark by John von Neumann about the difficulty of managing N people, which suggests that it arises essentially from 2-to-2 interactions, we define a "difficulty" function of an organization. The optimization of this organization is obtained by minimizing this function. This leads to different hierarchical structures depending on the discipline maintained. We also present a study of the "power" of a hierarchical organization. Finally, we compare these results with sociological studies of existing companies. Some analogies to physical theories are highlighted.
