Publications of Eric Bousquet
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See detailMagnetic phase diagram of rare-earth orthorhombic perovskite oxides
Sasani, Alireza ULiege; Iniguez, Jorge; Bousquet, Eric ULiege

in Physical review B (2021), 104(6), 064431-064446

Spin reorientation and magnetization reversal are two important features of the rare-earth orthorhombic perovskites (RMO3) that have attracted a lot of attention, though their exact microscopic origin has ... [more ▼]

Spin reorientation and magnetization reversal are two important features of the rare-earth orthorhombic perovskites (RMO3) that have attracted a lot of attention, though their exact microscopic origin has eluded researchers. Here, using density functional theory and classical atomistic spin dynamics we build a general Heisenberg magnetic model that allows to explore the whole phase diagram of the chromite and ferrite compounds and to scrutinize the microscopic mechanism responsible for spin reorientations and magnetization reversals. We show that the occurrence of a magnetization reversal transition depends on the relative strength and sign of two interactions between rare-earth and transition-metal atoms: superexchange and Dzyaloshinskii- Moriya. We also conclude that the presence of a smooth spin reorientation transition between the so-called G4 and the G2 phases through a coexisting region, and the temperature range in which it occurs, depends on subtle balance of metal-metal (superexchange and Dzyaloshinskii-Moriya) and metal–rare-earth (Dzyaloshinsky-Moriya) couplings. In particular, we show that the intermediate coexistence region occurs because the spin sublattices rotate at different rates. [less ▲]

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See detailNon-collinear magnetism & multiferroicity: the perovskite case
Bousquet, Eric ULiege; Cano, Andres

in Physical Sciences Reviews (2021)

The most important types of non-collinear magnetic orders that are realizedin simple perovskite oxides are outlined in relation to multiferroicity. These ordersare classified and rationalized in terms of ... [more ▼]

The most important types of non-collinear magnetic orders that are realizedin simple perovskite oxides are outlined in relation to multiferroicity. These ordersare classified and rationalized in terms of a mimimal spin Hamiltonian, based onwhich the notion of spin-driven ferroelectricity is illustrated. These concepts find di-rect application in reference materials such as BiFeO3,GdFeO3and TbMnO3whosemultiferroic properties are briefly reviewed. [less ▲]

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See detailTB2J: a python package for computing magnetic interaction parameters
He, Xu; Helbig, Nicole ULiege; Verstraete, Matthieu ULiege et al

in Computer Physics Communications (2021)

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See detailOptimized Methodology for the Calculation of Electrostriction from First-Principles
Tanner, Daniel ULiege; Bousquet, Eric ULiege; Janolin, Pierre-Eymeric

in Small (2021)

In this work a new method for the calculation of the electrostrictive proper- ties of materials using density functional theory is presented. The method relies on the thermodynamical equivalence, in a ... [more ▼]

In this work a new method for the calculation of the electrostrictive proper- ties of materials using density functional theory is presented. The method relies on the thermodynamical equivalence, in a dielectric, of the quadratic mechanical responses (stress or strain) to applied electric stimulus (elec- tric or polarization fields) to the strain or stress dependence of its dielec- tric susceptibility or stiffness tensors. Comparing with current finite-field methodologies for the calculation of electrostriction, it is demonstrated that this presented methodology offers significant advantages of effi- ciency, obustness, and ease of use. These advantages render tractable the high throughput theoretical investigation into the largely unknown electrostrictive properties of materials, and the microscopic origins of giant electrostriction. [less ▲]

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See detailUltrafast control of magnetic interactions via light-driven phonons
Afanasiev, D.; Hortensius, J. R.; Ivanov, B. A. et al

in Nature Materials (2021), 20

Resonant ultrafast excitation of infrared-active phonons is a powerful technique with which to control the electronic properties of materials that leads to remarkable phenomena such as the light-induced ... [more ▼]

Resonant ultrafast excitation of infrared-active phonons is a powerful technique with which to control the electronic properties of materials that leads to remarkable phenomena such as the light-induced enhancement of superconductivity1,2, switching of ferroelectric polarization3,4 and ultrafast insulator-to-metal transitions5. Here, we show that light-driven phonons can be utilized to coherently manipulate macroscopic magnetic states. Intense mid-infrared electric field pulses tuned to resonance with a phonon mode of the archetypical antiferromagnet DyFeO3 induce ultrafast and long-living changes of the fundamental exchange interaction between rare-earth orbitals and transition metal spins. Non-thermal lattice control of the magnetic exchange, which defines the stability of the macroscopic magnetic state, allows us to perform picosecond coherent switching between competing antiferromagnetic and weakly ferromagnetic spin orders. Our discovery emphasizes the potential of resonant phonon excitation for the manipulation of ferroic order on ultrafast timescales6. [less ▲]

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See detailFerroelectricity and multiferroicity in anti-Ruddlesden-Popper structures
Markov, M.; Alaerts, L.; Miranda, H.P.C. et al

in Proceedings of the National Academy of Sciences of the United States of America (2021), 118

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See detailOxyfluoride superlattices KTaO3/KMF3 (M=Zn, Ni): Structural and electronic phenomena
Garcia-Castro, A. C.; Ghosez, Philippe ULiege; Bousquet, Eric ULiege et al

in Physical Review. B (2020), 102

The structural and electronic properties of KTaO3/KZnF3 and KTaO3/KNiF3 oxyfluoride superlattices are studied from first-principles density functional theory calculations. We highlight, that beyond a ... [more ▼]

The structural and electronic properties of KTaO3/KZnF3 and KTaO3/KNiF3 oxyfluoride superlattices are studied from first-principles density functional theory calculations. We highlight, that beyond a critical layer thickness, these systems exhibit an insulator to metal transition that gives rise to the appearance of two- dimensional electron and hole gas, confined both, due the band alignment, within the oxide layer. The origin of the insulator to metal transition is related to the polar discontinuity at the interfaces. The behavior is discussed in terms of a simple electrostatic model and compared to that of the prototypical LaAlO3/SrTiO3 oxide system. The magnetic properties KTaO3/KNiF3 superlattices are further discussed, revealing a sizable Rashba-type spin splitting at these interfaces, much larger than in similar oxide/oxide systems. [less ▲]

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See detailUltrafast strain engineering and coherent structural dynamics from resonantly driven optical phonons in LaAlO3
Hortensius, J. R.; Afanasiev, D.; Sasani, Alireza ULiege et al

in npj Quantum Materials (2020), 5

Strain engineering has been extended recently to the picosecond timescales, driving ultrafast metal–insulator phase transitions and the propagation of ultrasonic demagnetization fronts. However, the ... [more ▼]

Strain engineering has been extended recently to the picosecond timescales, driving ultrafast metal–insulator phase transitions and the propagation of ultrasonic demagnetization fronts. However, the nonlinear lattice dynamics underpinning interfacial optoelectronic phase switching have not yet been addressed. Here we perform time-resolved all-optical pump-probe experiments to study ultrafast lattice dynamics initiated by impulsive light excitation tuned in resonance with a polar lattice vibration in LaAlO3 single crystals, one of the most widely utilized substrates for oxide electronics. We show that ionic Raman scattering drives coherent rotations of the oxygen octahedra around a high-symmetry crystal axis. By means of DFT calculations we identify the underlying nonlinear phonon–phonon coupling channel. Resonant lattice excitation is also shown to generate longitudinal and transverse acoustic wave packets, enabled by anisotropic optically induced strain. Importantly, shear strain wave packets are found to be generated with high efficiency at the phonon resonance, opening exciting perspectives for ultrafast material control. [less ▲]

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See detailFirst-principles characterization of single-electron polaron in WO3
Bousquet, Eric ULiege; Hamdi, Hanen; Aguado-Puente, Pablo et al

in Physical Review Research (2020), 2

Polarons are physical objects of material science that are hard to capture from first-principles calculations. WO3 is a paradigmatic system to study polarons and here we present calculations of a single ... [more ▼]

Polarons are physical objects of material science that are hard to capture from first-principles calculations. WO3 is a paradigmatic system to study polarons and here we present calculations of a single self-trapped single polaron in WO3 from density functional theory calculations. Our calculations show that the single polaron is at a higher energy than the fully delocalized solution, in agreement with the experiments where a single polaron is an excited state of WO3. The symmetry-adapted mode decomposition of the polaron distortions shows that, among numerous modes, a polar zone center mode has the largest contribution and can be at the origin of the observed weak ferroelectricity of WO3. [less ▲]

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See detailPyProcar: A Python library for electronic structure pre/post-processing
Herath, Uthpala; Tavadze, Pedram; He, Xu et al

in Computer Physics Communications (2020), 251

The PyProcar Python package plots the band structure and the Fermi surface as a function of site and/or s,p,d,f - projected wavefunctions obtained for each k-point in the Brillouin zone and band in an ... [more ▼]

The PyProcar Python package plots the band structure and the Fermi surface as a function of site and/or s,p,d,f - projected wavefunctions obtained for each k-point in the Brillouin zone and band in an electronic structure calculation. This can be performed on top of any electronic structure code, as long as the band and projection information is written in the PROCAR format, as done by the VASP and ABINIT codes. PyProcar can be easily modified to read other formats as well. This package is particularly suitable for understanding atomic effects into the band structure, Fermi surface, spin texture, etc. PyProcar can be conveniently used in a command line mode, where each one of the parameters define a plot property. In the case of Fermi surfaces, the package is able to plot the surface with colors depending on other properties such as the electron velocity or spin projection. The mesh used to calculate the property does not need to be the same as the one used to obtain the Fermi surface. A file with a specific property evaluated for each k-point in a k−mesh and for each band can be used to project other properties such as electron–phonon mean path, Fermi velocity, electron effective mass, etc. Another existing feature refers to the band unfolding of supercell calculations into predefined unit cells. [less ▲]

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See detailBi2W2O9: A potentially antiferroelectric Aurivillius phase
Djani-Ait, Hania ULiege; McCabe, Emma; Zhang, W. et al

in Physical Review. B (2020), 101

Ferroelectric tungsten-based Aurivillius oxides are naturally stable superlattice structures, in which A-site deficient perovskite blocks [Wn O3n+1 ]−2 (n = 1, 2, 3, . . . ) interleave with fluorite-like ... [more ▼]

Ferroelectric tungsten-based Aurivillius oxides are naturally stable superlattice structures, in which A-site deficient perovskite blocks [Wn O3n+1 ]−2 (n = 1, 2, 3, . . . ) interleave with fluorite-like bismuth oxide layers [Bi2O2]+2 along the c-axis. In the n = 2 Bi2W2O9 phase, an in-plane antipolar distortion dominates but there has been controversy as to the ground-state symmetry. Here we show, using a combination of first-principles density functional theory calculations and experiments, that the ground state is a nonpolar phase of Pnab symmetry. We explore the energetics of metastable phases and the potential for antiferroelectricity in this n = 2 Aurivillius phase. [less ▲]

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See detailRaman spectra of fine-grained materials from first principles
Popov, Maxim N.; Spitaler, Jürgen; Veerapandiyan, Vignaswaran K. et al

in npj Computational Materials (2020), 6

Raman spectroscopy is an advantageous method for studying the local structure of materials, but the interpretation of measured spectra is complicated by the presence of oblique phonons in polycrystals of ... [more ▼]

Raman spectroscopy is an advantageous method for studying the local structure of materials, but the interpretation of measured spectra is complicated by the presence of oblique phonons in polycrystals of polar materials. Whilst group theory considerations and standard ab initio calculations are helpful, they are often valid only for single crystals. In this paper, we introduce a method for computing Raman spectra of polycrystalline materials from first principles. We start from the standard approach based on the (Placzek) rotation invariants of the Raman tensors and extend it to include the effect of the coupling between the lattice vibrations and the induced electric field, and the electro-optic contribution, relevant for polar materials like ferroelectrics. As exemplified by applying the method to rhombohedral BaTiO3, AlN, and LiNbO3, such an extension brings the simulated Raman spectrum to a much better correspondence with the experimental one. Additional advantages of the method are that it is general, permits automation, and thus can be used in high-throughput fashion. [less ▲]

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See detailTuning between Proper and Hybrid-Improper Mechanisms for Polar Behavior in CsLn2Ti2NbO10 Dion-Jacobson Phases
Cascos, Vanessa A.; Roberts-Watts, J.; Skingle, C. et al

in Chemistry of Materials (2020), 32

The Dion-Jacobson (DJ) family of perovskite-related materials have recently attracted interest due to their polar structures and properties, resulting from hybrid-improper mechanisms for ferroelectricity ... [more ▼]

The Dion-Jacobson (DJ) family of perovskite-related materials have recently attracted interest due to their polar structures and properties, resulting from hybrid-improper mechanisms for ferroelectricity in n = 2 systems and from proper mechanisms in n = 3 CsBi2Ti2NbO10. We report here a combined experimental and computational study on analogous n = 3 CsLn2Ti2NbO10 (Ln = La, Nd) materials. Density functional theory calculations reveal the shallow energy landscape in these systems and give an understanding of the competing structural models suggested by neutron and electron diffraction studies. The structural disorder resulting from the shallow energy landscape breaks inversion symmetry at a local level, consistent with the observed second-harmonic generation. This study reveals the potential to tune between proper and hybrid-improper mechanisms by composition in the DJ family. The disorder and shallow energy landscape have implications for designing functional materials with properties reliant on competing low-energy phases such as relaxors and antiferroelectrics. [less ▲]

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See detailMaking EuO multiferroic by epitaxial strain engineering
Goian, Veronica; Held, Rainer; Bousquet, Eric ULiege et al

in Communications Materials (2020), 1

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See detailABINIT: Overview and focus on selected capabilities
Romero, Aldo ULiege; Allan, Douglas C.; Amadon, Bernard et al

in Journal of Chemical Physics (2020), 152(12), 124102

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See detailThe ABINIT project, impact, environment and recent developments
Gonze, Xavier; Amadon, Bernard; Antonius, Gabriel et al

in Computer Physics Communications (2020), 248

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See detailCanonical Jahn-Teller Distortion Notations: Understanding Structural-Electronic Interplays in e1g Perovskites
Schmitt, Michaël ULiege; Zhang, Yajun ULiege; Mercy, Alain ULiege et al

Scientific conference (2019, October 17)

In this talk we give a introduction to teh canonial jahn-teller distortion notations for perovskites experience metal-to-insulator transtition phenoma at elevated temperature.

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See detailAtomic-scale measurement of polar entropy
Mukherjee, Debangshu; Prokhorenko, Sergei ULiege; Miao, Leixin et al

in Physical Review. B, Condensed Matter (2019), 100

Entropy is a fundamental thermodynamic quantity that is a measure of the accessible microstates available to a system, with the stability of a system determined by the magnitude of the total entropy of ... [more ▼]

Entropy is a fundamental thermodynamic quantity that is a measure of the accessible microstates available to a system, with the stability of a system determined by the magnitude of the total entropy of the system. This is valid across truly mind boggling length scales, from nanoparticles to galaxies. However, quantitative measurements of entropy change using calorimetry are predominantly macroscopic, with direct atomic-scale measurements being exceedingly rare. Here, we experimentally quantify the polar configurational entropy (in meV/K) using sub-angstrom resolution aberration corrected scanning transmission electron microscopy in a single crystal of the prototypical ferroelectric LiNbO3 through the quantification of the niobium and oxygen atom column deviations from their paraelectric positions. Significant excursions of the niobium-oxygen polar displacement away from its symmetry-constrained direction are seen in single domain regions which increase in the proximity of domain walls. Combined with first-principles theory plus mean field effective Hamiltonian methods, we demonstrate the variability in the polar order parameter, which is stabilized by an increase in the magnitude of the configurational entropy. This study presents a powerful tool to quantify entropy from atomic displacements and demonstrates its dominant role in local symmetry breaking at finite temperatures in classic, nominally Ising ferroelectrics. [less ▲]

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See detailThe second-principles MULTIBINIT software project
Ricci, Fabio ULiege; Martin, Alexandre; Garcia Castro, Andrés Camilo et al

Conference (2019, March 08)

Detailed reference viewed: 52 (11 ULiège)