Publications

2021

• Experimental and theoretical analysis of vibrational modes in Fe(phen)2(NCS)2 single crystal
  
  • Privault Gaël
  • Gournay Lucas
  • Mevellec J Y
  • Corraze B
  • Chaban Ievgeniia F
  • Janod E
  • Lorenc Maciej
  • Daro N
  • Chastanet Guillaume
  • Humbert B
  • Subedi A
  • Collet Eric
  , 2021.
• Machine learning band gaps from the electron density
  
  • Moreno Javier Robledo
  • Flick Johannes
  • Georges Antoine
  Physical Review Materials, American Physical Society, 2021, 5 (8), pp.083802. A remarkable consequence of the Hohenberg-Kohn theorem of density functional theory is the existence of an injective map between the electronic density and any observable of the many-electron problem in an external potential. In this work, we study the problem of predicting a particular observable, the band gap of semiconductors and band insulators, from the knowledge of the local electronic density. Using state-of-the-art machine learning techniques, we predict the experimental band gaps from computationally inexpensive density functional theory calculations. We propose a modified Behler-Parrinello (BP) architecture that greatly improves the model capacity while maintaining the symmetry properties of the BP architecture. Using this scheme, we obtain band gaps at a level of accuracy comparable to those obtained with state-of-the-art and computationally intensive hybrid functionals, thus significantly reducing the computational cost of the task. (10.1103/PhysRevMaterials.5.083802)
  DOI : 10.1103/PhysRevMaterials.5.083802
• High-order expansion around BCS theory
  
  • Spada G.
  • Rossi R.
  • Simkovic F.
  • Garioud R.
  • Ferrero M.
  • van Houcke Kris
  • Werner Felix
  , 2021. We demonstrate that high-order diagrammatic expansion around BCS theory is a viable generic unbiased approach for strongly correlated fermions in superconducting or superfluid phases. For the 3D attractive Hubbard model in a strongly correlated regime, we observe convergence of the diagrammatic series, evaluated up to 12 loops thanks to the connected determinant diagrammatic Monte Carlo algorithm. Our study includes the polarized regime, where conventional quantum Monte Carlo methods suffer from the fermion sign problem. Upon increasing the Zeeman field, we observe the first-order superconducting-to-normal phase transition at low temperature, and a significant polarization of the superconducting phase at higher temperature. (10.48550/arXiv.2103.12038)
  DOI : 10.48550/arXiv.2103.12038
• Quench Spectroscopy of a Disordered Quantum System
  
  • Villa L.
  • Thomson S. J
  • Sanchez-Palencia L.
  Physical Review A, American Physical Society, 2021, 104 (2), pp.L021301. The characterization of excitations in disordered quantum systems is a central issue in connection with glass physics and many-body localization. Here, we show that quench spectroscopy of a disordered model, as realized from its out-of-equilibrium dynamics following a global quench, allows us to fully characterize the spectral properties of the disordered phases. In the Bose-Hubbard model, a clear signature of gapless excitations in momentum-resolved spectroscopy enables us to accurately locate the Mott insulator to Bose glass transition, while the presence or absence of a well-defined soundlike mode distinguishes the superfluid from the Bose glass phase. Moreover, spatially-resolved spectroscopy provides local spectral properties and allows us to extract the typical spacing of gapless regions, giving a second independent way to uniquely identify all three phases. Our findings have far-ranging implications for a variety of experimental platforms, and offer a powerful and versatile probe of the low-energy phases of disordered systems. (10.1103/PhysRevA.104.L021301)
  DOI : 10.1103/PhysRevA.104.L021301
• Finding the phase diagram of strongly correlated disordered bosons using quantum quenches
  
  • Villa L.
  • Thomson S. J
  • Sanchez-Palencia L.
  Physical Review A, American Physical Society, 2021, 104 (2). The question of how the low-energy properties of disordered quantum systems may be connected to exotic localization phenomena at high energy is a key open question in the context of quantum glasses and many-body localization. In Ref. [1], we have shown that key features of the excitation spectrum of a disordered system can be efficiently probed from out-of-equilibrium dynamics following a quantum quench, providing distinctive signatures of the various phases. Here, we extend this work by providing a more in-depth study of the behavior of the quench spectral functions associated to different observables and investigating an extended parameter regime. We provide a detailed introduction to quench spectroscopy for disordered systems and show how spectral properties can be probed using both local operators and two-point correlation functions. We benchmark the technique using the one-dimensional Bose-Hubbard model in the presence of a random external potential, focusing on the low-lying excitations, and demonstrate that quench spectroscopy can distinguish the Mott insulator, superfluid, and Bose glass phases. We then explicitly reconstruct the zero-temperature phase diagram of the disordered Bose-Hubbard at fixed filling using two independent methods, both experimentally accessible via time-of-flight imaging and quantum gas microscopy respectively, and demonstrate that quench spectroscopy can give valuable insights as to the distribution of rare regions within disordered systems. (10.1103/PhysRevA.104.023323)
  DOI : 10.1103/PhysRevA.104.023323
• Gluon transversity and TMDs for spin-1 hadrons
  
  • Kumano S.
  • Song Qin-Tao
  , 2022, 3 (3), pp.0308097. We explain a gluon transversity, transverse-momentum-dependent parton distribution functions (TMDs), and parton distribution functions (PDFs) for spin-1 hadrons. The gluon transversity exists in hadrons with spin more than or equal to one, and it does not exist in the spin-1/2 nucleons. Since there is no direct contribution from the nucleons, it is an appropriate quantity to probe an exotic component in the spin-1 deuteron beyond a simple bound system of the nucleons. We show how the gluon transversity can be measured at hadron accelerator facilities by the Drell-Yan process in addition to lepton-accelerator experiments. Next, possible TMDs are explained for the spin-1 hadrons at the twists 3 and 4 in addition to twist-2 ones by considering tensor polarizations. We found that 30 TMDs exist in the tensor-polarized spin-1 hadron at the twists 3 and 4 in addition to 10 TMDs at the twist 2. There are 3 collinear PDFs at the twists 3 and 4. We also indicate that the corresponding TMD fragmentation functions exist at the twists 3 and 4. Due to the time-reversal invariance in the collinear PDFs, there are new sum rules on the time-reversal odd TMDs. In addition, we obtained a useful twist-2 relation, a sum rule, and relations with multiparton distribution functions by using the operator product expansion and the equation of motion for quarks. These findings are valuable for experimental investigations on polarized deuteron structure functions in 2020's and 2030's at world accelerator facilities. (10.31349/SuplRevMexFis.3.0308097)
  DOI : 10.31349/SuplRevMexFis.3.0308097
• Remote triggering of air-gap discharge by a femtosecond laser filament and postfilament at distances up to 80 m
  
  • Kosareva O. G
  • Mokrousova D. V
  • Panov N. A
  • Nikolaeva I. A
  • Shipilo D. E
  • Mitina E. V
  • Koribut A. V
  • Rizaev G. E
  • Couairon A.
  • Houard Aurélien
  • Savel'Ev A. B
  • Seleznev L. V
  • Ionin A. A
  • Chin S. L
  Applied Physics Letters, American Institute of Physics, 2021, 119 (4), pp.041103. We experimentally observed laser-induced remote high-voltage discharge triggering between two needle electrodes with half-a-cm spacing. The discharge was initiated by a 744-nm, 90-fs, 6-mJ laser pulse undergoing filamentation in air. For the direct voltage below the self-breakdown threshold, triggering of air-gap discharge was synchronized with a 10-Hz laser repetition rate and occurred between 40 and 80 m of the propagation path. No discharge guiding was observed. The experimentally registered and simulated remote triggering probability was above 80% in the range of 45–60 m from laser output and about 50% in the range of 60–80 m. The probability decreases as the postfilament hot spot diverges with a simultaneous increase in stochastic laser beam wandering. (10.1063/5.0057544)
  DOI : 10.1063/5.0057544
• En route to realistic modeling of the kinetic-MHD interaction between macroscopic modes and fast particles induced by neutral beam injection in tokamaks
  
  • Orain F
  • Brochard G
  • Nicolas Timothee
  • Lütjens H
  • Garbet X
  • Dumont R
  • Maget P
  , 2021. A new model of fast ion source induced by Neutral Beam Injection (NBI) in tokamaks has been implemented in the hybrid kinetic-magnetohydrodynamic code XTOR-K. This source, combined with the collisions also recently implemented, allows for the modeling of realistic slowing-down populations and their interplay with macroscopic modes. This paper describes the Neutral Beam injection and ionization model designed to reproduce experimental configurations and its validation for a typical discharge of the ASDEX Upgrade tokamak. The application to the interaction of NBI-induced fast particles with a kink mode in ASDEX Upgrade demonstrates a resonance between passing particles and the n = 1 mode. This resonance partially stabilizes the kink mode and induces a radial transport of fast particles. Preliminary results in ITER-like circular geometry show that NBI induces a toroidal torque but has little impact on the kink mode dynamics.
• Stripes, Antiferromagnetism, and the Pseudogap in the Doped Hubbard Model at Finite Temperature
  
  • Wietek Alexander
  • He Yuan-Yao
  • White Steven
  • Georges Antoine
  • Stoudenmire E. Miles
  Physical Review X, American Physical Society, 2021, 11 (3), pp.031007. (10.1103/PhysRevX.11.031007)
  DOI : 10.1103/PhysRevX.11.031007
• The importance of multiple scatterings in medium-induced gluon radiation
  
  • Andres Carlota
  • Dominguez Fabio
  • Martinez Marcos Gonzalez
  , 2022, 10, pp.016. In this work we disentangle the underlying physical picture of the in-medium gluon radiation process across its different energy regimes by comparing the recently obtained fully-resummed -- without any further approximations -- BDMPS-Z in-medium emission spectrum with the extensively used analytical approaches. We observe that in the high-energy regime the radiation process is dominated by a single hard scattering, while in the intermediate-energy region coherence effects among multiple scatterings are crucial. Finally, we prove that in the low-energy regime the dynamics is again controlled by a single scattering but where one must include a suppression factor accounting for the probability of not having any further scatterings. (10.21468/SciPostPhysProc.10.016)
  DOI : 10.21468/SciPostPhysProc.10.016
• Out-of-equilibrium dynamics and quench spectroscopy of ultracold many-body quantum systems
  
  • Villa Louis
  , 2021. Ultracold atoms have emerged as a versatile platform to realise and control strongly-correlated quantum systems. Spectroscopic methods are the common tools to probe the properties of the excitations which control dynamical transport phenomena.In this thesis, we develop a novel spectroscopic method named quench spectroscopy that uses the out-of-equilibrium dynamics generated by a quantum quench to grant momentum-resolved information about the excitations. We benchmark the method on one-dimensional models where efficient density matrix renormalisation group numerical simulations are available.First, we analyse the out-of-equilibrium space-time pattern of quantum correlations in lattice models following a quantum quench. It displays a generic light-cone like pattern with a twofold structure. Two characteristic velocities can be extracted from the correlations close to the cone edge, one of which gives the velocity for the propagation of quantum correlations throughout the system. Both of these velocities can be related to dynamical properties of the excitation spectrum of the underlying model.Second, we discuss how quench spectroscopy reconstructs spectral properties from space-time patterns using simple equal-time observables or correlators. It allows to reconstruct the full dispersion relation from a series of snapshots of the experiment using quantum gas microscopes, and avoids the tedious scan and calibration in momentum necessary in standard pump-probe methods. We investigate both global and local quenches on clean systems, and discuss the role played by the observable on the spectral features. We discuss the implementation on various examples including the Bose-Hubbard model and spin chain models in various phases, regimes and for different observables.Third, we extend quench spectroscopy to disordered systems. Using as an example the disordered Bose-Hubbard chain, we show using a single probe how the method can unambiguously tell apart the Bose glass from the Mott insulator and the superfluid. Using a spatially-resolved spectral probe, we also reconstruct the full phase diagram of the model. (10.70675/a34e166azf662z47b3z9372z2c0f861b719a)
  DOI : 10.70675/a34e166azf662z47b3z9372z2c0f861b719a
• Black hole S-matrix for a scalar field
  
  • Betzios Panos
  • Gaddam Nava
  • Papadoulaki Olga
  Journal of High Energy Physics, Springer, 2021, 2021 (7), pp.17. A bstract We describe a unitary scattering process, as observed from spatial infinity, of massless scalar particles on an asymptotically flat Schwarzschild black hole background. In order to do so, we split the problem in two different regimes governing the dynamics of the scattering process. The first describes the evolution of the modes in the region away from the horizon and can be analysed in terms of the effective Regge-Wheeler potential. In the near horizon region, where the Regge-Wheeler potential becomes insignificant, the WKB geometric optics approximation of Hawking’s is replaced by the near-horizon gravitational scattering matrix that captures non-perturbative soft graviton exchanges near the horizon. We perform an appropriate matching for the scattering solutions of these two dynamical problems and compute the resulting Bogoliubov relations, that combines both dynamics. This allows us to formulate an S-matrix for the scattering process that is manifestly unitary. We discuss the analogue of the (quasi)-normal modes in this setup and the emergence of gravitational echoes that follow an original burst of radiation as the excited black hole relaxes to equilibrium. (10.1007/JHEP07(2021)017)
  DOI : 10.1007/JHEP07(2021)017
• Geometry of orientifold vacua and supersymmetry breaking
  
  • Coudarchet Thibaut
  • Dudas Emilian
  • Partouche Hervé
  Journal of High Energy Physics, Springer, 2021, 2021. A bstract Starting from a peculiar orientifold projection proposed long ago by Angelantonj and Cardella, we elaborate on a novel perturbative scenario that involves only D-branes, together with the two types of orientifold planes O ± and anti-orientifold planes $$ {\overline{\mathrm{O}}}_{\pm } $$ O ¯ ± . We elucidate the microscopic ingredients of such models, connecting them to a novel realization of brane supersymmetry breaking. Depending on the position of the D-branes in the internal space, supersymmetry can be broken at the string scale on branes, or alternatively only at the massive level. The main novelty of this construction is that it features no NS-NS disk tadpoles, while avoiding open-string instabilities. The one-loop potential, which depends on the positions of the D-branes, is minimized for maximally broken, non-linearly realized supersymmetry. The orientifold projection and the effective field theory description reveal a soft breaking of supersymmetry in the closed-string sector. In such models it is possible to decouple the gravitino mass from the value of the scalar potential, while avoiding brane instabilities. (10.1007/JHEP07(2021)104)
  DOI : 10.1007/JHEP07(2021)104
• Correlation-induced octahedral rotations in SrMoO 3
  
  • Hampel Alexander
  • Lee-Hand Jeremy
  • Georges Antoine
  • Dreyer Cyrus
  Physical Review B, American Physical Society, 2021, 104 (3), pp.035102. (10.1103/PhysRevB.104.035102)
  DOI : 10.1103/PhysRevB.104.035102
• Impact of partially bosonized collective fluctuations on electronic degrees of freedom
  
  • Harkov V.
  • Vandelli M.
  • Brener S.
  • Lichtenstein A.
  • Stepanov E.
  Physical Review B, American Physical Society, 2021, 103 (24), pp.245123. (10.1103/PhysRevB.103.245123)
  DOI : 10.1103/PhysRevB.103.245123
• Correlated electronic structure and optical response of rare-earth based semiconductors
  
  • Galler Anna
  • Boust James
  • Demourgues Alain
  • Biermann Silke
  • Pourovskii Leonid V.
  Physical Review B, American Physical Society, 2021, 103 (24), pp.L241105 (6 p.). The coexistence of Mott localized f states with wide conduction and valence bands in f-electron semiconductors results, quite generically, in a complex optical response with the nature of the absorption edge difficult to resolve both experimentally and theoretically. Here, we combine a dynamical mean-field theory approach to localized 4f shells with an improved description of band gaps by a semilocal exchange-correlation potential to calculate the optical properties of the light rare-earth fluorosulfides LnSF (Ln=Pr, Nd, Sm, Gd) from first principles. In agreement with experiment, we find the absorption edge in SmSF to stem from S−3p to Sm−4f transitions, while the Gd compound behaves as an ordinary p−d gap semiconductor. In the unexplored PrSF and NdSF systems we predict a rather unique occurrence of strongly hybridized 4f−5d states at the bottom of the conduction band. The nature of the absorption edge results in a characteristic anisotropy of the optical conductivity in each system, which may be used as a fingerprint of the relative energetic positions of different states. (10.1103/physrevb.103.l241105)
  DOI : 10.1103/physrevb.103.l241105
• u-Channel Color Transparency Observables
  
  • Huber G. M.
  • Li W. B.
  • Cosyn W.
  • Pire B.
  , 2022, 4, pp.451–461. We propose to study the onset of color transparency in hard exclusive reactions in the backward regime. Guided by the encouraging JLab results on backward pion and omega electro-production data at moderate Q^2, which may be interpreted as the signal of an early scaling regime where the scattering amplitude factorizes in a hard coefficient function convoluted with nucleon to meson transition distribution amplitudes, we show that the study of these channels on nuclear targets opens a new opportunity to test the appearance of nuclear color transparency for a fast moving nucleon.
• The Status and Future of Color Transparency and Nuclear Filtering
  
  • Jain Pankaj
  • Pire Bernard
  • Ralston John P.
  , 2022, 4 (2), pp.578-589. Fourty years after its introduction, the phenomenon of color transparency remains a domain of controversial interpretations of experimental data. In this review, present evidence for or against color transparency manifestation in various exclusive hard scattering reactions is presented. The nuclear transparency experiments reveal whether short-distance processes dominate a scattering amplitude at some given kinematical point. We plead for a new round of nuclear transparency measurements in a variety of experimental set-ups, including near-forward exclusive reactions related to generalized parton distribution (GPD) physics and near-backward exclusive reactions related to transition distribution amplitudes (TDA) physics. (10.3390/physics4020038)
  DOI : 10.3390/physics4020038
• Exploring the Foundations of the Physical Universe with Space Tests of the Equivalence Principle
  
  • Battelier Baptiste
  • Bergé Joël
  • Bertoldi Andrea
  • Blanchet Luc
  • Bongs Kai
  • Bouyer Philippe
  • Braxmaier Claus
  • Calonico Davide
  • Fayet Pierre
  • Gaaloul Naceur
  • Guerlin Christine
  • Hees Aurelien
  • Jetzer Philippe
  • Lämmerzahl Claus
  • Lecomte Steve
  • Le Poncin-Lafitte Christophe
  • Loriani S.
  • Métris Gilles
  • Nofrarias M.
  • Rasel Ernst
  • Reynaud Serge
  • Rodrigues Manuel
  • Rothacher Markus
  • Roura Albert
  • Salomon Christophe
  • Schiller Stephan
  • Schleich Wolfgang P.
  • Schubert C.
  • Sopuerta Carlos
  • Sorrentino Fiodor
  • Sumner Tim J.
  • Tino Guglielmo M.
  • Tuckey Philip
  • von Klitzing Wolf
  • Wörner Lisa
  • Wolf Peter
  • Zelan Martin
  Experimental Astronomy, Springer Link, 2021, 51 (3), pp.1695-1736. We present the scientific motivation for future space tests of the equivalence principle, and in particular the universality of free fall, at the 10− 17 level or better. Two possible mission scenarios, one based on quantum technologies, the other on electrostatic accelerometers, that could reach that goal are briefly discussed. This publication is a White Paper written in the context of the Voyage 2050 ESA Call for White Papers. (10.1007/s10686-021-09718-8)
  DOI : 10.1007/s10686-021-09718-8
• Diffractive rho plus lepton pair production at an electron-ion collider
  
  • Cosyn W.
  • Pire B.
  Physical Review D, American Physical Society, 2021, 103, pp.114002. In high energy electron-ion colliders, a new way to probe nucleon structure becomes available through diffractive reactions, where the incident particle produces a very energetic almost forward particle. QCD describes these reactions as due to the exchange of a Pomeron which may be perturbatively described as a dressed two-gluon state, provided a hard scale allows the factorization of the amplitude in terms of two impact factors convoluted with a Pomeron propagator. We consider here a process where such a description allows to access hadronic structure in terms of the generalized parton distributions, namely the electroproduction of a forward rho meson and a timelike deeply virtual photon, separated by a large rapidity gap. We explore the dependence of the cross section on the kinematic variables and study the dependence on the non-perturbative inputs (generalized parton distributions, distribution amplitude). Our leading order studies show the cross section is mainly sensitive to the GPD model input, but the small size of the cross sections could prohibit straightforward analysis of this process at planned facilities.
• Spontaneous chiral symmetry breaking in the massive Landau gauge: realistic running coupling
  
  • Peláez Marcela
  • Reinosa Urko
  • Serreau Julien
  • Tissier Matthieu
  • Wschebor Nicolás
  Physical Review D, American Physical Society, 2021. We investigate the spontaneous breaking of chiral symmetry in QCD by means of a recently proposed approximation scheme in the Landau-gauge Curci-Ferrari model, which combines an expansion in the Yang-Mills coupling and in the inverse number of colors, without expanding in the quark-gluon coupling. The expansion allows for a consistent treatment of ultraviolet tails via renormalization group techniques. At leading order, it leads to the resummation of rainbow diagrams for the quark propagator, with, however, a trivial running of both the gluon mass and the quark-gluon coupling. In a previous work, by using a simple model for a more realistic running of these parameters, we could reproduce the known phenomenology of chiral symmetry breaking, including a satisfactory description of the lattice data for the quark mass function. Here, we get rid of this model-dependence by taking our approximation scheme to next-to-leading order. This allows us to consistently include the realistic running of the parameters and to access the unquenched gluon and ghost propagators to first nontrivial order, which we can compare to available lattice data for an even more stringent test of our approach. In particular, our results for the various two-point functions compare well with lattice data while the parameters of the model are strongly constrained.
• Gauge fixing and field redefinitions of the Hartle--Hawking wavefunction path integral
  
  • Partouche Hervé
  • Toumbas Nicolaos
  • de Vaulchier Balthazar
  , 2021. We review some recent results concerning the Hartle--Hawking wavefunction of the universe. We focus on pure Einstein theory of gravity in the presence of a positive cosmological constant. We carefully implement the gauge-fixing procedure for the minisuperspace path integral, by identifying the single modulus and by using diffeomorphism-invariant measures for the ghosts and the scale factor. Field redefinitions of the scale factor yield different prescriptions for computing the no-boundary ground-state wavefunction. They give rise to an infinite set of ground-state wavefunctions, each satisfying a different Wheeler--DeWitt equation, at the semi-classical level. The differences in the form of the Wheeler--DeWitt equations can be traced to ordering ambiguities in constructing the Hamiltonian upon canonical quantization. However, the inner products of the corresponding Hilbert spaces turn out to be equivalent, at least semi-classically. Thus, the model yields universal quantum predictions.
• Gauge invariance of transverse momentum dependent distributions at small x
  
  • Boussarie Renaud
  • Mehtar-Tani Yacine
  Physical Review D, American Physical Society, 2021, 103 (9), pp.094012. (10.1103/PhysRevD.103.094012)
  DOI : 10.1103/PhysRevD.103.094012
• SU($N$) Cartan-Weyl bases and color factors
  
  • van Egmond Duifje Maria
  • Reinosa Urko
  , 2021. Constant temporal backgrounds have become a convenient tool for the discussion of continuum non-abelian gauge theories at finite temperature, as they provide a grasp on the confinement/deconfinement transition. It has been pointed that such backgrounds are better dealt with within so-called Cartan-Weyl color bases, rather than within the standard Cartesian bases. Here, we discuss the specificities of the evaluation of SU($N$) color factors within these bases, extending the discussion in Ref. [1].
• Collisional vertical f -asymmetry effect
  
  • Maget P
  • Frank J
  • Manas P
  • Dumont R
  • Nicolas T
  • Artaud J-F
  • Bourdelle C
  • Colas L
  • Goniche M
  • Agullo O
  • Garbet X
  • Lütjens H
  , 2021. The use of metallic walls as plasma facing components in tokamaks puts severe constraints on the control of impurity contamination. Heavy impurities like Tungsten are of particular concern due to the high level of radiative losses they can induce. Moreover, their high sensitivity to neoclassical transport mechanisms exacerbated by toroidal rotation or electrostatic potential asymmetry generally explains experimental cases of strong accumulation in the plasma core. The poloidal distribution of the impurity modulates the amplitude of this neoclassical transport [Angioni14], with an asymmetry that often leads to enhancement, but that can also result in a reduction of the flux