References of "Physical Review Letters"
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See detailConstraining Effective Field Theories with Machine Learning
Brehmer, Johann; Cranmer, Kyle; Louppe, Gilles ULiege et al

in Physical Review Letters (2018)

We present powerful new analysis techniques to constrain effective field theories at the LHC. By leveraging the structure of particle physics processes, we extract extra information from Monte-Carlo ... [more ▼]

We present powerful new analysis techniques to constrain effective field theories at the LHC. By leveraging the structure of particle physics processes, we extract extra information from Monte-Carlo simulations, which can be used to train neural network models that estimate the likelihood ratio. These methods scale well to processes with many observables and theory parameters, do not require any approximations of the parton shower or detector response, and can be evaluated in microseconds. We show that they allow us to put significantly stronger bounds on dimension-six operators than existing methods, demonstrating their potential to improve the precision of the LHC legacy constraints. [less ▲]

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See detailDirect magnetization-polarization coupling in BaCuF4
García Castro, Andrès Camilo ULiege; Ibarra-Hernandez, Wilfredo; Bousquet, Eric ULiege et al

in Physical Review Letters (2018), 121

Herewith, first-principles calculations based on density functional theory are used to describe the ideal magnetization reversal through polarization switching in BaCuF4 which, according to our results ... [more ▼]

Herewith, first-principles calculations based on density functional theory are used to describe the ideal magnetization reversal through polarization switching in BaCuF4 which, according to our results, could be accomplished close to room temperature. We also show that this ideal coupling is driven by a single soft mode that combines both polarization, and octahedral rotation. The later being directly coupled to the weak ferromagnetism of BaCuF4. This, added to its strong Jahn-Teller distortion and its orbital ordering, makes this material a very appealing prototype for crystals in the ABX4 family for multifunctional applications. The described mechanism behaves ideally as it couples the ferroelectric and the magnetic properties naturally and it has not been reported previously. [less ▲]

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See detailScaling Theory of the Anderson Transition in Random Graphs: Ergodicity and Universality
Garcia-Mata, Ignacio; Giraud, Olivier; Georgeot, Bertrand et al

in Physical Review Letters (2017), 118

We study the Anderson transition on a generic model of random graphs with a tunable branching parameter 1 < K < 2, through large scale numerical simulations and finite-size scaling analysis. We find that ... [more ▼]

We study the Anderson transition on a generic model of random graphs with a tunable branching parameter 1 < K < 2, through large scale numerical simulations and finite-size scaling analysis. We find that a single transition separates a localized phase from an unusual delocalized phase that is ergodic at large scales but strongly nonergodic at smaller scales. In the critical regime, multifractal wave functions are located on a few branches of the graph. Different scaling laws apply on both sides of the transition: a scaling with the linear size of the system on the localized side, and an unusual volumic scaling on the delocalized side. The critical scalings and exponents are independent of the branching parameter, which strongly supports the universality of our results. [less ▲]

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See detailZhao et al. Reply
Zhao, J. Z.; Fan, W.; Verstraete, Matthieu ULiege et al

in Physical Review Letters (2017), 118(23), 239602

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See detailQuantitative Agreement between Electron-Optical Phase Images of $WSe_2$ and Simulations Based on Electrostatic Potentials that Include Bonding Effects
Borghardt, S.; Winkler, F.; Zanolli, Zeila ULiege et al

in Physical Review Letters (2017), 118

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See detailEmergent Berezinskii-Kosterlitz-Thouless Phase in Low-Dimensional Ferroelectrics
Nahas, Yousra ULiege; Prokhorenko, Sergei ULiege; Kornev, I. et al

in Physical Review Letters (2017), 119(11),

Using first-principles-based simulations merging an effective Hamiltonian scheme with scaling, symmetry, and topological arguments, we find that an overlooked Berezinskii-Kosterlitz-Thouless (BKT) phase ... [more ▼]

Using first-principles-based simulations merging an effective Hamiltonian scheme with scaling, symmetry, and topological arguments, we find that an overlooked Berezinskii-Kosterlitz-Thouless (BKT) phase sustained by quasicontinuous symmetry emerges between the ferroelectric phase and the paraelectric one of BaTiO3 ultrathin film, being under tensile strain. Not only do these results provide an extension of BKT physics to the field of ferroelectrics, but they also unveil their nontrivial critical behavior in low dimensions. © 2017 American Physical Society. [less ▲]

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See detailUnveiling the Room-Temperature Magnetoelectricity of Troilite FeS
Ricci, Fabio ULiege; Bousquet, Eric ULiege

in Physical Review Letters (2016), 116

We report on a first-principles study of the troilite phase of iron sulfide (FeS). We show that even if, a few decades ago, this material was thought to be ferroelectric, the structural transition from ... [more ▼]

We report on a first-principles study of the troilite phase of iron sulfide (FeS). We show that even if, a few decades ago, this material was thought to be ferroelectric, the structural transition from the high P63/mmc to the low P6¯2c symmetry phase does not involve polar instabilities, though the space inversion center symmetry is broken. Our calculations and symmetry analysis nevertheless reveal that FeS is magnetoelectric at room temperature with a response larger than the prototypical room-temperature magnetoelectric crystal Cr2O3. We also show that the spin channel decomposition of the polarization exhibits nonzero values in the opposite direction in FeS, which is actually a general hint of the presence of a magnetoelectric monopole in diagonal magnetoelectrics. [less ▲]

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See detailTwo-step phase transition in SnSe and the origins of its high power factor from first principles
Dewandre, Antoine ULiege; Hellman, Olle; Bhattacharya, Sandip et al

in Physical Review Letters (2016), 117

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See detailQuasi-One-Dimensional Metal-Insulator Transitions in Compound Semiconductor Surfaces
Zhao, J. Z.; Fan, W.; Verstraete, Matthieu ULiege et al

in Physical Review Letters (2016), 117

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See detailStrain-Engineered Multiferroicity in Pnma NaMnF3 Fluoroperovskite
Garcia Castro, Andrés Camilo ULiege; Romero, Aldo H.; Bousquet, Eric ULiege

in Physical Review Letters (2016), 116

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See detailElectric Field Control of Jahn-Teller Distortions in Bulk Perovskites
Varignon, Julien ULiege; Bristowe, Nicholas ULiege; Ghosez, Philippe ULiege

in Physical Review Letters (2016), 116

The Jahn-Teller distortion, by its very nature, is often at the heart of the various electronic properties displayed by perovskites and related materials. Despite the Jahn-Teller mode being nonpolar, we ... [more ▼]

The Jahn-Teller distortion, by its very nature, is often at the heart of the various electronic properties displayed by perovskites and related materials. Despite the Jahn-Teller mode being nonpolar, we devise and demonstrate, in the present Letter, an electric field control of Jahn-Teller distortions in bulk perovskites. The electric field control is enabled through an anharmonic lattice mode coupling between the Jahn-Teller distortion and a polar mode. We confirm this coupling and quantify it through first-principles calculations. The coupling will always exist within the Pb21m space group, which is found to be the favored ground state for various perovskites under sufficient tensile epitaxial strain. Intriguingly, the calculations reveal that this mechanism is not only restricted to Jahn-Teller active systems, promising a general route to tune or induce novel electronic functionality in perovskites as a whole. [less ▲]

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See detailDisplacement of an Electrically Charged Drop on a Vibrating Bath
Brandenbourger, Martin ULiege; Vandewalle, Nicolas ULiege; Dorbolo, Stéphane ULiege

in Physical Review Letters (2016), 116

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See detailTensor Representation of Spin States
Giraud, Olivier; Braun, Daniel; Baguette, Dorian ULiege et al

in Physical Review Letters (2015), 114

We propose a generalization of the Bloch sphere representation for arbitrary spin states. It provides a compact and elegant representation of spin density matrices in terms of tensors that share the most ... [more ▼]

We propose a generalization of the Bloch sphere representation for arbitrary spin states. It provides a compact and elegant representation of spin density matrices in terms of tensors that share the most important properties of Bloch vectors. Our representation, based on covariant matrices introduced by Weinberg in the context of quantum field theory, allows for a simple parametrization of coherent spin states, and a straightforward transformation of density matrices under local unitary and partial tracing operations. It enables us to provide a criterion for anticoherence, relevant in a broader context such as quantum polarization of light. [less ▲]

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See detailBeyond-Standard-Model Tensor Interaction and Hadron Phenomenology
Courtoy, Aurore ULiege; Baeßler, Stefan; González–Alonso, Martín et al

in Physical Review Letters (2015), 115(16), 162001

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See detailCoherent electronic wave packet motion in c60 controlled by the waveform and polarization of few-cycle laser fields
Li, H.; Mignolet, Benoît ULiege; Wachter, G. et al

in Physical Review Letters (2015), 114(12), 123004

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See detailLow-Dimensional Transport and Large Thermoelectric Power Factors in Bulk Semiconductors by Band Engineering of Highly Directional Electronic States
Bilc, Daniel ULiege; Hautier, Geoffroy; Waroquiers, David et al

in Physical Review Letters (2015), 114

Thermoelectrics are promising for addressing energy issues but their exploitation is still hampered by low efficiencies. So far, much improvement has been achieved by reducing the thermal conductivity but ... [more ▼]

Thermoelectrics are promising for addressing energy issues but their exploitation is still hampered by low efficiencies. So far, much improvement has been achieved by reducing the thermal conductivity but less by maximizing the power factor. The latter imposes apparently conflicting requirements on the band structure: a narrow energy distribution and a low effective mass. Quantum confinement in nanostructures andtheintroductionofresonantstatesweresuggestedaspossiblesolutionstothisparadox,butwithlimited success. Here, we propose an original approach to fulfill both requirements in bulk semiconductors. It exploits the highly directional character of some orbitals to engineer the band structure and produce a type of low-dimensional transport similar to that targeted in nanostructures, while retaining isotropic properties. Using first-principle calculations, the theoretical concept is demonstrated in Fe2YZ Heusler compounds, yielding power factors 4 to 5 times larger than in classical thermoelectrics at room temperature. Our findings are totally generic and rationalize the search of alternative compounds with similar behavior. Beyond thermoelectricity, these might be relevant also in the context of electronic, superconducting, or photovoltaic applications. [less ▲]

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See detailStrain Induced Vortex Core Switching in Planar Magnetostrictive Nanostructures
Ostler, Thomas ULiege; Cuadrado, R.; Chantrell, R. W. et al

in Physical Review Letters (2015), 115(6), 067202

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See detailTwo Scenarios for Quantum Multifractality Breakdown
Dubertrand, Rémy ULiege; Garcia-Mata, Ignacio; Georgeot, Bertrand et al

in Physical Review Letters (2014), 112

We expose two scenarios for the breakdown of quantum multifractality under the effect of perturbations. In the first scenario, multifractality survives below a certain scale of the quantum fluctuations ... [more ▼]

We expose two scenarios for the breakdown of quantum multifractality under the effect of perturbations. In the first scenario, multifractality survives below a certain scale of the quantum fluctuations. In the other one, the fluctuations of the wave functions are changed at every scale and each multifractal dimension smoothly goes to the ergodic value. We use as generic examples a one-dimensional dynamical system and the three-dimensional Anderson model at the metal-insulator transition. Based on our results, we conjecture that the sensitivity of quantum multifractality to perturbation is universal in the sense that it follows one of these two scenarios depending on the perturbation. We also discuss the experimental implications. [less ▲]

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See detailAre Hydrogen-Bonded Charge Transfer Crystals Room Temperature Ferroelectrics?
D'Avino, Gabriele ULiege; Verstraete, Matthieu ULiege

in Physical Review Letters (2014), 113

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See detailCoherent Backscattering in Fock Space: A Signature of Quantum Many-Body Interference in Interacting Bosonic Systems
Engl, Thomas; Dujardin, Julien ULiege; Argüelles, Arturo et al

in Physical Review Letters (2014), 112

We predict a generic signature of quantum interference in many-body bosonic systems resulting in a coherent enhancement of the average return probability in Fock space. This enhancement is robust with ... [more ▼]

We predict a generic signature of quantum interference in many-body bosonic systems resulting in a coherent enhancement of the average return probability in Fock space. This enhancement is robust with respect to variations of external parameters even though it represents a dynamical manifestation of the delicate superposition principle in Fock space. It is a genuine quantum many-body effect that lies beyond the reach of any mean-field approach. Using a semiclassical approach based on interfering paths in Fock space, we calculate the magnitude of the backscattering peak and its dependence on gauge fields that break time-reversal invariance. We confirm our predictions by comparing them to exact quantum evolution probabilities in Bose-Hubbard models, and discuss their relevance in the context of many-body thermalization. [less ▲]

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