Publications

2022

• Absence of evidence for entanglement in a three-photon Greenberger-Horn-Zeilinger type experiment
  
  • Coddens Gerrit
  , 2022. A famous experiment by Pan et al. (Nature 403, 515 (2000)) on a three-photon Bell state is considered to prove the existence of entanglement without relying on Bell inequalities. We show that the theory this proof is based on contains errors in the calculations that are beyond repair. Indeed, the formalism to describe the internal dynamics of electrons (at rest) and photons in quantum mechanics is based on the representations of the rotation group. For electrons, who have spin 1/2, the representation is SU(2), for photons, who have spin 1 it is SO(2). Rotations are just a subject of elementary Euclidean geometry, which does not contain any physics, let alone "quantum magic". Therefore all quantum paradoxes that oppose classical mechanics and QM (when it is purely based on the algebra of SU(2)), can only be due to logical errors and a lack of understanding of the group representation theory. The three-photon Bell state is extended but not non-local and as such does not imply a "spooky action at a distance". (This version supersedes the previous version which contained an error).
• Screening effect in spin Hall devices
  
  • Olive E
  • Wegrowe Jean-Eric
  • Creff M
  Physical Review B, American Physical Society, 2022, 105 (17), pp.174419. The stationary state of the spin Hall bar is studied in the framework of a variational approach that includes nonequilibrium screening effects at the edges. The minimization of the power dissipated in the system is performed taking into account the spin-flip relaxation and the global constraints due to the electric generator and global charge conservation. The calculation is performed within the approximations of negligible spin-flip scattering and strong spin-flip scattering. In both cases, simple expressions of the spin accumulation and the longitudinal and transverse pure spin currents are derived analytically. In usual conditions, the maximum amplitude of the spin accumulation is expected to be of the order of 1% of the equilibrium density carriers. (10.1103/physrevb.105.174419)
  DOI : 10.1103/physrevb.105.174419
• Derivation of Malus' law by purely classical reasoning expressed in the language of group representation theory
  
  • Coddens Gerrit
  , 2022. This work is part of a reconstruction of quantum mechanics from scratch with the aim to understand what it means. In previous work we have shown that the Dirac equation can be derived by classical reasoning just using relativity and group theory. This implies that contrary to common belief quantum mechanics (QM) is not magical or radically different from classical mechanics. It is also not incompatible with the theory of relativity but completely part of it. As the experimental violations of the Bell inequalities seem to take exception with this general scheme for making sense of QM we have scrutinized the derivation of the Bell inequalities to figure out the limitations of our approach. We were able to show that the derivation contains a logical error based on wrong modelling. In the present paper we complete this investigation by showing that Malus' law can be derived by classical reasoning using group representation theory, both for electrons and photons. This is a further, be it somewhat more indirect proof that the derivation of the Bell inequalities contains an error. But more importantly it shows that the philosophy of our approach remains intact, by proving that we can also understand Malus' law with our methods and thereby validating our approach also for this physical phenomenon.
• Strontium release from wollastonite-based brushite cement paste under semi-dynamic leaching conditions
  
  • Jdaini Jihane
  • Cau dit Coumes Céline
  • Barré Yves
  • de Noirfontaine Marie-Noëlle
  • Courtial Mireille
  • Garcia-Caurel Enrique
  • Dunstetter Frédéric
  • Gorse-Pomonti Dominique
  , 2022.
• Modification of β-gallium oxide electronic properties by irradiation with high-energy electrons
  
  • Dang T.-Huong
  • Konczykowski M.
  • Jaffrès H.
  • Safarov V I
  • Drouhin H.-J.
  Journal of Vacuum Science & Technology A, American Vacuum Society, 2022, 40 (3), pp.033416. We present a study of the modifications of the electronic properties of β-gallium oxide crystals by 2.5-MeV electron irradiation. This type of irradiation produces exclusively local point defects in Ga 2 O 3 , predominantly gallium vacancies, which act as acceptor centers. Starting with a highly n-doped sample, we establish a quantitative linear relation between the irradiation dose and the concentration of generated acceptor centers. This gives the possibility to tune the Fermi level position within the bandgap by choosing an appropriate irradiation dose. At high doses, with a very deep position of the Fermi level, the n-type sample becomes compensated, reaching a semi-insulating state. The downward shift of the Fermi level with irradiation allows us to reveal the presence of latent impurities of transition metals (like Cr and Fe), which are inactive in electron paramagnetic resonance and luminescence spectra of pristine samples. This study confirms the potential of electron irradiation as a tool for tailoring the electronic properties of gallium oxide. (10.1116/6.0001821)
  DOI : 10.1116/6.0001821
• Effect of Magnetic Fields on the Microwave Impedance of FeCoB + SiO2 Composite Films
  
  • Kotov L.
  • Lasek M.
  • Vlasov V.
  • Utkin A.
  • Kalinin Yu.
  • Sitnikov A.
  • Temnov V.
  Bulletin of the Russian Academy of Sciences - Physics, Springer Verlag/Russian Academy of Sciences (RAS), 2022, 86 (5), pp.588-591. (10.3103/S1062873822050136)
  DOI : 10.3103/S1062873822050136
• O2 Loaded Germanosilicate Optical Fibers: Experimental In Situ Investigation and Ab Initio Simulation Study of GLPC Evolution under Irradiation
  
  • Reghioua Imene
  • Giacomazzi Luigi
  • Alessi Antonino
  • Winkler Blaz
  • Martin-Samos Layla
  • Girard Sylvain
  • Di Francesca Diego
  • Fanetti Mattia
  • Richard Nicolas
  • Paillet Philippe
  • Raine Melanie
  • Agnello Simonpietro
  • Valant Matjaz
  • Boukenter Aziz
  • Ouerdane Youcef
  Applied Sciences, Multidisciplinary digital publishing institute (MDPI), 2022, 12 (8), pp.3916. In this work we present a combined experimental and ab initio simulation investigation concerning the Germanium Lone Pair Center (GLPC), its interaction with molecular oxygen (O2), and evolution under irradiation. First, O2 loading has been applied here to Ge-doped optical fibers to reduce the concentration of GLPC point defects. Next, by means of cathodoluminescence in situ experiments, we found evidence that the 10 keV electron irradiation of the treated optical fibers induces the generation of GLPC centers, while in nonloaded optical fibers, the irradiation causes the bleaching of the pre-existing GLPC. Ab initio calculations were performed to investigate the reaction of the GLPC with molecular oxygen. Such investigations suggested the stability of the dioxagermirane (DIOG) bulk defect, and its back conversion into GLPC with a local release of O2 under irradiation. Furthermore, it is also inferred that a remarkable portion of the O2 passivated GLPC may form Ge tetrahedra connected to peroxy bridges. Such structures may have a larger resistance to the irradiation and not be back converted into GLPC. (10.3390/app12083916)
  DOI : 10.3390/app12083916
• Room-temperature superfluorescence in hybrid perovskites and its origins
  
  • Biliroglu Melike
  • Findik Gamze
  • Mendes Juliana
  • Seyitliyev Dovletgeldi
  • Lei Lei
  • Dong Qi
  • Mehta Yash
  • Temnov Vasily
  • So Franky
  • Gundogdu Kenan
  Nature Photonics, Nature Publishing Group, 2022, 16 (4), pp.324-329. (10.1038/s41566-022-00974-4)
  DOI : 10.1038/s41566-022-00974-4
• Boron carbide under torsional deformation: evidence of the formation of chain vacancies in the plastic regime
  
  • Chakraborti Amrita
  • Jay Antoine
  • Hardouin Duparc Olivier
  • Sjakste Jelena
  • Béneut Keevin
  • Vast Nathalie
  • Le Godec Yann
  Acta Materialia, Elsevier, 2022, 226, pp.117553. We report a combined experimental and theoretical study of boron carbide under stress/deformation. A special rotating anvil press, the rotating tomography Paris Edinburgh cell (RoToPEC), has been used to apply torsional deformation to boron carbide under a pressure of 5 GPa at ambient temperature. Subsequent damages and point defects have been analysed at ambient pressure by energy dispersive X-ray microdiffraction at the synchrotron and by Raman spectroscopy, combined with calculations based on the density functional theory (DFT). We show that apart from the signals due to B4C, new peaks appear in both characterisation methods. The DFT calculations of atomic structures and phonon frequencies enable us to attribute most of the new peaks to boron vacancies in the intericosahedral chains of boron carbide. Some of the Raman spectra also show three peaks that have been attributed to amorphous boron carbide in the literature. Deformed boron carbide thus shows small inclusions of clusters of boron carbide with chain vacancies, and/or small zones interpreted as amorphous zones (10.1016/j.actamat.2021.117553)
  DOI : 10.1016/j.actamat.2021.117553
• Improving NV centre density during diamond growth by CVD process using N2O gas
  
  • Ngambou Midrel Wilfried Ngandeu
  • Pellet-Mary Clément
  • Brinza Ovidiu
  • Antonino Alessi
  • Hetet Gabriel
  • Tallaire Alexandre
  • Bénédic Fabien
  • Achard Jocelyn
  Diamond and Related Materials, Elsevier, 2022, 123, pp.108884. Nitrogen-vacancy (NV) centres in diamond are point-like defects that have attracted a lot of attention as promising candidates for quantum technologies particularly for sensing and imaging nanoscale magnetic fields. For this application, the use of a high NV density within a high-quality diamond layer is of prime interest. In previous works, it has been demonstrated that in situ doping with N2O rather than N2 during chemical vapour deposition (CVD), limits the formation of macroscopic defects and improves NV's photostability. In this work, we focus on the optimization of the CVD growth conditions to obtain a high NV density keeping a constant N2O concentration in the gas phase (100 ppm). For this purpose, freestanding CVD layers are prepared varying two main growth parameters: methane content and substrate temperature. High energy electron irradiation followed by annealing is finally carried out in order to increase the NV yield through partial conversion of N impurities. Defect concentrations and spin properties are investigated. We find that growth under lower methane concentrations and lower temperatures enhances NV doping. NV ensembles with a density of the order of 2 ppm are finally obtained with narrow spin resonance linewidth. In addition, higher annealing temperatures of 1200 °C following irradiation are found to efficiently remove defects thus improving spin properties. (10.1016/j.diamond.2022.108884)
  DOI : 10.1016/j.diamond.2022.108884
• Possible unconventional pairing in (Ca,Sr)$_3$ (Ir,Rh)$_4$Sn$_{13}$ superconductors revealed by controlling disorder
  
  • Krenkel E H
  • Tanatar M A
  • Kończykowski M.
  • Grasset R.
  • Timmons E I
  • Ghimire S.
  • Joshi K R
  • Lee Y.
  • Ke Liqin
  • Chen Shuzhang
  • Petrovic C.
  • Orth P P
  • Scheurer M S
  • Prozorov R.
  Physical Review B, American Physical Society, 2022, 105 (9), pp.094521. We study the evolution of temperature-dependent resistivity with added pointlike disorder induced by 2.5 MeV electron irradiation in stoichiometric compositions of the “3-4-13” stannides, (Ca,Sr)3(Ir,Rh)4Sn13. Three of these cubic compounds exhibit a proposed microscopic coexistence of charge density wave (CDW) order and superconductivity (SC), while Ca3Rh4Sn13 does not develop CDW order. As expected, the CDW transition temperature TCDW is universally suppressed by irradiation in all three compositions. The superconducting transition temperature, Tc, behaves in a more complex manner. In Sr3Rh4Sn13, it increases initially in a way consistent with a direct competition of CDW and SC, but quickly saturates at higher irradiation doses. In the other three compounds, Tc is monotonically suppressed by irradiation. The strongest suppression is found in Ca3Rh4Sn13, which does not have CDW order. We further examine this composition by measuring the London penetration depth λ(T ), from which we derive the superfluid density. The result unambiguously points to a weak-coupling, full single gap, isotropic superconducting state. Therefore we must explain two seemingly incompatible experimental observations: a single isotropic superconducting gap and a significant suppression of Tc by nonmagnetic disorder. We conduct a quantitative theoretical analysis based on a generalized Anderson theorem which points to an unconventional multiband s+−-pairing state where the sign of the order parameter is different on one (or a small subset) of the smaller Fermi surface sheets but remains isotropic and overall fully gapped. (10.1103/PhysRevB.105.094521)
  DOI : 10.1103/PhysRevB.105.094521
• Hot electron relaxation and energy loss rate in silicon: Temperature dependence and main scattering channels
  
  • Sen R.
  • Vast Nathalie
  • Sjakste Jelena
  Applied Physics Letters, American Institute of Physics, 2022, 120 (8), pp.082101. In this work, we revisit the density functional theory (DFT)-based results for electron–phonon scattering in highly excited silicon. Using the state-of-the-art ab initio methods, we examine the main scattering channels, which contribute to the total electron–phonon scattering rate and the energy loss rate of photoexcited electrons in silicon as well as their temperature dependence. Both temperature dependence and the main scattering channels are shown to strongly differ for the total electron–phonon scattering rate and the energy loss rate of photoexcited electrons. While the total electron–phonon scattering rate increases strongly with temperature, the temperature dependence of the energy loss rate is negligible. Also, while acoustic phonons dominate the total electron–phonon scattering rate at 300 K, the main contribution to the energy loss rate comes from optical modes. In this respect, DFT-based results are found to disagree with conclusions of Fischetti et al. [Appl. Phys. Lett. 114, 222104 (2019)]. We explain the origin of this discrepancy, which is mainly due to differences in the description of the electron–phonon scattering channels associated with transverse phonons. (10.1063/5.0082727)
  DOI : 10.1063/5.0082727
• Quantum mechanics with only real numbers
  
  • Coddens Gerrit
  , 2022. We show that every Clifford algebra can be transformed into a formalism that uses only real numbers. The rules we must follow to achieve this are universal. To illustrate the method we construct the real pendant of SU(2) and we derive a version of the Dirac equation that uses only real numbers. The advantage of the complex formulations is that they reduce the size of the representation matrices by a factor of 2. The reason for the presence of complex numbers in quantum mechanics is that it is formulated in the language of group representation theory.
• Recombination time mismatch and spin dependent photocurrent at a ferromagnetic-metal/semiconductor tunnel junction
  
  • Safarov Viatcheslav I
  • Rozhansky Igor V
  • Zhou Ziqi
  • Xu Bo
  • Wei Zhongming
  • Wang Zhan-Guo
  • Lu Yuan
  • Jaffrès Henri
  • Drouhin Henri-Jean
  Physical Review Letters, American Physical Society, 2022, 128 (5), pp.057701. We report on carrier dynamics in a spin photodiode based on a ferromagnetic-metal–GaAs tunnel junction. We show that the helicity-dependent current is determined not only by the electron spin polarization and spin asymmetry of the tunneling but in great part by a dynamical factor resulting from the competition between tunneling and recombination in the semiconductor, as well as by a specific quantity: the charge polarization of the photocurrent. The two latter factors can be efficiently controlled through an electrical bias. Under longitudinal magnetic field, we observe a strong increase of the signal arising from inverted Hanle effect, which is a fingerprint of its spin origin. Our approach represents a radical shift in the physical description of this family of emerging spin devices. (10.1103/PhysRevLett.128.057701)
  DOI : 10.1103/PhysRevLett.128.057701
• A novel shortcut for computational materials design
  
  • Aouina Ayoub
  , 2022. Density functional theory (DFT) tells us that any property of an interacting system is a functional of the ground-state electronic density. The Kohn-Sham scheme has made DFT a practical computational tool to study the electronic structure of materials. The main quantity that needs to be approximated is the exchange correlation (xc) potential. In the local density approximation (LDA), the real system is treated locally as a homogeneous electrons gas (HEG) with a density equal to the local density of the real system. The xc potential is then imported locally from the HEG, which serves as a model. It has been obtained, once for all, by accurate quantum Monte Carlo calculations (QMC) of the HEG at various densities. These calculations contributed immensely to the success of DFT being one of the most widely used method for modelling solids and molecules.Inspired by the LDA and the use of the HEG, in this thesis we generalise the idea of using models to simulate real systems. Our approach, called "Connector Theory" (COT), is an in principle exact prescription of how to use data from models to calculate quantities in materials. The power of this approach is twofold: first, starting from an in principle exact theory provides a guideline to build systematic and improvable approximations. Second, since models are usually simpler systems, one can also afford high level calculations with great precision for new model quantities. The benefit is enormous since these calculations are done once and for all and serve as building blocks to approximate real quantities.After introducing the general scheme of COT, we used it to build non-local functionals of the density for the xc potential, starting from a linear expansion. We showed that the LDA can be derived as a particular case of the COT approximation. In order to test the COT strategy, we applied it to reproduce a non-local functional of the xc potential based on the weighted density approximation. The results were very promising: on the one hand, we could obtain the LDA within the COT scheme by making the Coulomb interaction short range. On the other hand, we constructed a non-local description of the functional that goes beyond the LDA and the linear expansion. To examine the COT approximation of the xc potential, we implemented it in the self-consistent Kohn-Sham loop and computed the electronic densities of silicon, a semiconductor, and sodium chloride, an insulator. When compared to benchmark QMC results, the densities produced from this COT xc potential were very accurate. This was due to the ability of COT functional to capture a significant amount of the non-local information of the system.Independently of the COT, we have examined the inverse question of obtaining the xc potential from the accurate QMC density. The main aim was to analyse the features of the exact xc potential and to compare them with the COT and other DFT approximations. We addressed various technical issues related to the algorithm of the inversion, which was applied for the first time in solids, including the influence of the basis set and the statistical error of QMC. The inverted xc potential enabled us to determine the exact xc energies, Kohn-Sham band gaps and band structures of Si and NaCl, and to benchmark corresponding COT approximations. This also provided the motivation to build and test a new COT functional optimised for the xc energy.Finally, we demonstrated that COT is not limited to DFT by using it to estimate the density without diagonalising an independent-particle Hamiltonian. We have also explained how to use COT to approximate non-local objects such as the density matrix; in this example, we showed that a non-homogenous model can boost COT approximations. These more complex models could be calculated using nowadays computer capacities, and the results could be interpolated and parametrised using available machine learning techniques.
• The Modern Problems of Ultrafast Magnetoacoustics (Review)
  
  • Vlasov V.
  • Golov A.
  • Kotov L.
  • Shcheglov V.
  • Lomonosov A.
  • Temnov Vasily
  Acoustical Physics / Akusticheskii zhurnal, MAIK Nauka/Interperiodica, 2022, 68 (1), pp.18-47. (10.1134/S1063771022010079)
  DOI : 10.1134/S1063771022010079
• Effect of high-energy electron irradiation on the electronic properties of beta-gallium oxide
  
  • Dang Thi-Huong
  • Konczykowski Marcin
  • Safarov Viatcheslav
  • Hammou Elie
  • Romero Vega Lucia
  • Ollier Nadège
  • Grasset Romain
  • Alessi Antonino
  • Drouhin Henri-Jean
  • Jaffrès Henri
  • Davydov Valery
  • Wołoś Agnieszka
  • Rogers David
  • Sandana Vinod
  • Bove Philippe
  • Teherani Féréchteh
  , 2022, pp.60. (10.1117/12.2622559)
  DOI : 10.1117/12.2622559
• Electron Dynamics in Hybrid Perovskites Reveal the Role of Organic Cations on the Screening of Local Charges
  
  • Cherasse Marie
  • Dong Jingwei
  • Trippé-Allard Gaëlle
  • Deleporte Emmanuelle
  • Garrot Damien
  • Maehrlein Sebastian
  • Wolf Martin
  • Chen Zhesheng
  • Papalazarou Evangelos
  • Marsi Marino
  • Rueff Jean-Pascal
  • Taleb-Ibrahimi Amina
  • Perfetti Luca
  Nano Letters, American Chemical Society, 2022, 22 (5), pp.2065-2069. The large tolerance of hybrid perovksites to the trapping of electrons by defects is a key asset in photovoltaic applications. Here, the ionic surface terminations of CH3NH3PbI3 are employed as a testbed to study the effect of electrostatic fields on the dynamics of excited carriers. We characterize the transition across the tetragonal to orthorhombic phase. The observed type II band offset and drift of the excited electrons highlight the important role that organic cations have on the screening of local electrostatic fields. When the orientation of organic cations is frozen in the orthorhombic phase, the positively charged termination induces a massive accumulation of excited electrons at the surface of the sample. Conversely, no electron accumulation is observed in the tetragonal phase. We conclude that the local fields cannot penetrate in the sample when the polarizability of freely moving cations boosts the dielectric constant up to ϵ = 120. (10.1021/acs.nanolett.2c00001)
  DOI : 10.1021/acs.nanolett.2c00001
• Visualizing the effects of plasma-generated H atoms <i>in situ</i> in a transmission electron microscope
  
  • Maurice Jean-Luc
  • Bulkin Pavel
  • Ngo Éric
  • Wang Weixi
  • Foldyna Martin
  • Florea Ileana
  • Roca I Cabarrocas Pere
  • Béjaud Romuald
  • Hardouin Duparc Olivier
  European Physical Journal: Applied Physics, EDP Sciences, 2022, 97, pp.7. The radicals and atoms generated by a plasma have the effect, among others, of changing the surface energies of materials, which allows one to prepare nano-objects that would not stabilise in other conditions. This is the case of the Sn catalysed silicon nanowires (NWs) we present in this paper: without plasma, the liquid Sn at the top of NWs is unstable (because Sn naturally wets the Si) so that no growth is allowed, while in presence of the H atoms generated by the plasma, the balance of surface energies is drastically changed; the Sn droplet stabilises and can be used efficiently by the vapour-liquid-solid (VLS) mechanism of growth. Thus, if one wants to study the growth mechanisms of such NWs in situ in the transmission electron microscope (TEM), one has to adapt a plasma system on the TEM. This is precisely what was done at École polytechnique on the NanoMAX environmental TEM. The paper reports on the plasma effects, on the catalyst and on NW growth, recorded in situ in real time, at atomic resolution. The results are discussed in the light of density functional calculations of bare and hydrogenated Si surface energies. (10.1051/epjap/2022210276)
  DOI : 10.1051/epjap/2022210276
• Cu precipitation in electron-irradiated iron alloys for spent-fuel canisters
  
  • Yang Qigui
  • Chang Zhongwen
  • Messina Luca
  • Sandberg Nils
  • Castin Nicolas
  • Yousfi Amine
  • Toijer Elin
  • Thuvander Mattias
  • Boizot Bruno
  • Metayer Vincent
  • Gorse-Pomonti Dominique
  • Olsson Pär
  Journal of Nuclear Materials, Elsevier, 2022, 572, pp.154038. In this work, the Cu clustering in Fe under irradiation is investigated using experiments, cluster dynamics and atomistic kinetic Monte Carlo (AKMC) simulations. In experiments, cast iron and model FeCu alloy samples were irradiated with 2 MeV electrons for 143 h at 140 °C. The post-irradiation microstructure was characterized using atom probe tomography. Cluster dynamics and AKMC methods were used to simulate the Cu clustering under the same irradiation conditions. Both simulation methods show satisfactory agreement with experiments, lending strength to the validity of the models. Finally, the Cu clustering in spent-fuel repository conditions for 10$^5$ years at 100 °C was simulated using both methods. The results indicate that potential hardening by Cu clustering is insignificant over 10$^5$ years. (10.1016/j.jnucmat.2022.154038)
  DOI : 10.1016/j.jnucmat.2022.154038
• Multiband superconductivity in V$_3$Si determined from studying the response to controlled disorder
  
  • Cho Kyuil
  • Kończykowski M.
  • Ghimire S.
  • Tanatar M A
  • Wang Lin-Lin
  • Kogan V G
  • Prozorov R.
  Physical Review B, American Physical Society, 2022, 105 (2), pp.024506. The London penetration depth λ(T ) was measured in a single crystal of V3Si. The superfluid density obtained from this measurement shows a distinct signature of two almost decoupled superconducting gaps. This alone is insufficient to distinguish between s± and s++ pairing states, but it can be achieved by studying the effect of controlled nonmagnetic disorder on the superconducting transition temperature Tc. For this purpose, the same V3Si crystal was sequentially irradiated by 2.5-MeV electrons three times, repeating the measurement between the irradiation runs. A total dose of 10 C/cm2 (6.24 × 1019 electrons/cm2) was accumulated, for which Tc changed from 16.4 K in a pristine state to 14.7 K (9.3%). Not only is this substantial suppression impossible for a single isotropic gap, but also it is not large enough for a sign-changing s± pairing state. Our electronic band structure calculations show how five bands crossing the Fermi energy can be naturally grouped to support two effective gaps, not dissimilar from the physics of iron pnictides. We analyze the results using two-gap models for both λ(T ) and Tc which describe the data very well. Thus the experimental results and theoretical analysis provide strong support for an s++ superconductivity with two unequal gaps, 1(0) ≈ 2.53 meV and 2 (0) ≈ 1.42 meV, and a very weak interband coupling in the V3Si superconductor. (10.1103/PhysRevB.105.024506)
  DOI : 10.1103/PhysRevB.105.024506
• DFT Exchange: Sharing Perspectives on the Workhorse of Quantum Chemistry and Materials Science
  
  • Teale Andrew Michael
  • Helgaker Trygve
  • Savin Andreas
  • Adano Carlo
  • Aradi Bálint
  • Arbuznikov Alexei
  • Ayers Paul
  • Baerends Evert Jan
  • Barone Vincenzo
  • Calaminici Patrizia
  • Cances Eric
  • Carter Emily Ann
  • Chattaraj Pratim
  • Chermette Henry
  • Ciofini Ilaria
  • Crawford T. Daniel
  • de Proft Frank
  • Dobson John
  • Draxl Claudia
  • Frauenheim Thomas
  • Fromager Emmanuel
  • Fuentealba Patricio
  • Gagliardi Laura
  • Galli Giulia
  • Gao Jiali
  • Geerlings Paul
  • Gidopoulos Nikitas
  • Gill Peter
  • Gori-Giorgi Paola
  • Görling Andreas
  • Gould Tim
  • Grimme Stefan
  • Gritsenko Oleg
  • Jensen Hans Jørgen Aagaard
  • Johnson Erin
  • Jones Robert
  • Kaupp Martin
  • Koster Andreas
  • Kronik Leeor
  • Krylov Anna
  • Kvaal Simen
  • Laestadius Andre
  • Levy Melvyn
  • Lewin Mathieu
  • Liu Sb
  • Loos Pierre-Francois
  • Maitra Neepa
  • Neese Frank
  • Perdew John
  • Pernal Katarzyna
  • Pernot Pascal
  • Piecuch P.
  • Rebolini Elisa
  • Reining Lucia
  • Romaniello Pina
  • Ruzsinszky Adrienn
  • Salahub Dennis
  • Scheffler Matthias
  • Schwerdtfeger Peter
  • Staroverov Viktor
  • Sun Jianwei
  • Tellgren Erik
  • Tozer David
  • Trickey Samuel
  • Ullrich Carsten
  • Vela Alberto
  • Vignale Giovanni
  • Wesolowski Tomasz Adam
  • Xu Xin
  • Yang Weitao
  Physical Chemistry Chemical Physics, Royal Society of Chemistry, 2022, 24 (47), pp.28700-28781. In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method... (10.1039/D2CP02827A)
  DOI : 10.1039/D2CP02827A
• Intermediate scattering potential strength in electron-irradiated YBa$_2$Cu$_3$O$_{7−δ}$ from London penetration depth measurements
  
  • Cho Kyuil
  • Kończykowski M.
  • Teknowijoyo S.
  • Ghimire S.
  • Tanatar M A
  • Mishra Vivek
  • Prozorov R.
  Physical Review B, American Physical Society, 2022, 105, pp.014514. Temperature-dependent London penetration depth, λ(T ), of a high quality optimally doped YBa2Cu3O7−δ single crystal was measured using a tunnel-diode resonator. Controlled artificial disorder was induced at a low temperature of 20 K by 2.5 MeV electron irradiation with the accumulation of large doses of 3.8 × 1019 and 5.3 × 1019 electrons per cm2. The irradiation caused significant suppression of the superconductor’s critical temperature, Tc, from 94.6 to 90.0 K and then to 78.7 K, respectively. The low-temperature behavior of λ(T ) evolves from a T linear in pristine state to a T 2 behavior after the irradiation, expected for a line-nodal d-wave superconductor. However, the original theory that explained such behavior had assumed a unitary limit of the scattering potential, whereas usually in normal metals and semiconductors, Born scattering is sufficient to describe the experiment. To estimate the scattering potential strength, we calculated the normalized superfluid density, ρs(t = T/Tc ) = λ2(0)/λ2 (t), varying the amount and the strength of nonmagnetic scattering using a self-consistent t-matrix theory. Fitting the obtained curves to a power law, ρs = 1 − Rt n, and to a polynomial, ρs = 1 − At − Bt 2, and comparing the coefficients n in one set and A and B in another with the experimental values, we estimate the phase shift to be around 70 and 65◦, respectively. We correlate this result with the evolution of the density of states with nonmagnetic disorder. (10.1103/PhysRevB.105.014514)
  DOI : 10.1103/PhysRevB.105.014514
• Lumière et électromagnétisme au prisme de l’amitié entre Fresnel et Ampère
  
  • Amouyal Edmond
  Reflets de la Physique, EDP sciences, 2022 (72), pp.38-43. La théorie ondulatoire de la lumière d’Augustin Fresnel et celle de l’électrodynamique d’André-Marie Ampère, sont les fruits d’une véritable collaboration -peu connue- entre deux savants, courageux face aux tenants des théories dominantes, fidèles en amitié et géniaux. Elles constituent deux des plus grandes découvertes du XIXème siècle, survenues durant l’admirabile tempus 1815-1820. (10.1051/refdp/202272038)
  DOI : 10.1051/refdp/202272038
• Time-resolved structural dynamics of the out-of-equilibrium charge density wave phase transition in GdTe 3
  
  • González-Vallejo I
  • Jacques V L R
  • Boschetto D
  • Rizza G
  • Hadj-Azzem A
  • Faure Jérôme
  • Le Bolloc'H D
  Structural Dynamics, AIP Publishing, 2022, 9 (1), pp.014502. We use ultrafast electron diffraction (UED) to study the out-of-equilibrium dynamics of the charge density wave (CDW) phase transition in GdTe3, a quasi-two-dimensional compound displaying a unidirectional CDW state. Experiments were conducted at different incident fluences and different initial sample temperatures below Tc. We find that following photo-excitation, the system undergoes a non-thermal ultrafast phase transition that occurs in out-of-equilibrium conditions. The intrinsic crystal temperature was estimated at each time delay from the atomic thermal motion which affects each Bragg peak intensity via the Debye Waller factor. Assuming an isotropic harmonic potential, we estimate the out-of-equilibrium temperature Tqe as a function of the laser fluence. We then relate the recovery time constants and correlation lengths as a function of Tqe. The charge density wave is suppressed in less than a picosecond and recovers the long range order with increasing recovery times with increasing fluences and increasing initial temperatures. The measured relaxation times are discussed in terms of the Rothwarf-Taylor model. If indeed, the recovery time increases for initial temperatures closer to Tc in agreement with the model, this one cannot however explain the slowness of the system to return to its ground state. In addition, the transient CDW phase recently observed along the transverse direction in LaTe3 and CeTe3 is not observed in GdTe3. (10.1063/4.0000131)
  DOI : 10.1063/4.0000131