Elemental Pr metal is unique among rare-earth elements in featuring a localized partially filled 4f shell without ordered magnetism.Experimental evidence attributes this absence of magnetismto a singlet crystal-field(...Elemental Pr metal is unique among rare-earth elements in featuring a localized partially filled 4f shell without ordered magnetism.Experimental evidence attributes this absence of magnetismto a singlet crystal-field(CF)ground state of the Pr 4f^(2) configuration.Here,we construct an effective magnetic Hamiltonian for dhcp Pr,by combining density-functional theory with dynamical mean-field theory,in the quasiatomic Hubbard-I approximation.Our calculations fully determine the CF potential and predict singlet CF ground states for both inequivalent Pr sites.The intersite exchange interactions,obtained from the magnetic force theorem,are insufficient to close the CF gap to the magnetic doublets.Hence,ab-initio theory is demonstrated to explain the non-magnetic state of elemental Pr.We also find that the singlet ground state remains robust preventing conventional magnetic orders at the(0001)surface of Pr.Nevertheless,the gap between the ground state and the lowest excited singlet is significantly reduced at the surface,opening the possibility for exotic two-dimensional multipolar orders to emerge within this two-singlet manifold.展开更多
Laser–plasma interaction and hot electrons have been characterized in detail in laser irradiation conditions relevant for direct-drive inertial confinement fusion.The experiment was carried out at the Gekko XII laser...Laser–plasma interaction and hot electrons have been characterized in detail in laser irradiation conditions relevant for direct-drive inertial confinement fusion.The experiment was carried out at the Gekko XII laser facility in multibeam planar target geometry at an intensity of approximately 3×10^(15)W/cm^(2).Experimental data suggest that high-energy electrons,with temperatures of 20–50 keV and conversion efficiencies ofη<1%,were mainly produced by the damping of electron plasma waves driven by two-plasmon decay(TPD).Stimulated Raman scattering(SRS)is observed in a near-threshold growth regime,producing a reflectivity of approximately 0.01%,and is well described by an analytical model accounting for the convective growth in independent speckles.The experiment reveals that both TPD and SRS are collectively driven by multiple beams,resulting in a more vigorous growth than that driven by single-beam laser intensity.展开更多
The structural phase transition in Ta-NiSes has been envisioned as driven by the formation of an excitonic insulating phase.However,the role of structural and electronic instabilities on crystal symmetry breaking has ...The structural phase transition in Ta-NiSes has been envisioned as driven by the formation of an excitonic insulating phase.However,the role of structural and electronic instabilities on crystal symmetry breaking has yet to be disentangled.Meanwhile,the phase transition in its complementary material Ta_(2)NiS_(5)does not show any experimental hints of an excitonic insulating phase.We present a microscopic investigation of the electronic and phononic effects involved in the structural phase transition in Ta_(2)NiSe_(5)and Ta-Niss using extensive first-principles calculations.In both materials the crystal symmetries are broken by phonon instabilities,which in tum lead to changes in the electronic bandstructure also observed in the experiment.A total energy landscape analysis shows no tendency towards a purely electronic instability and we find that a sizeable lattice distortion is needed to open a bandgap.We conclude that an excitonic instability is not needed to explain the phase transition in both Ta_(2)NiSe_(5)and Ta_(2)NiS_(5).展开更多
We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility,aimed at investigating laser±plasma interaction in conditions that are of interest for the shock ignition s...We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility,aimed at investigating laser±plasma interaction in conditions that are of interest for the shock ignition scheme in inertial confinement fusion(ICF),that is,laser intensity higher than 10^(16) W/cm^(2) impinging on a hot(T>1 keV),inhomogeneous and long scalelength pre-formed plasma.Measurements show a significant stimulated Raman scattering(SRS)backscattering(;%-20%of laser energy)driven at low plasma densities and no signatures of two-plasmon decay(TPD)/SRS driven at the quarter critical density region.Results are satisfactorily reproduced by an analytical model accounting for the convective SRS growth in independent laser speckles,in conditions where the reflectivity is dominated by the contribution from the most intense speckles,where SRS becomes saturated.Analytical and kinetic simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non-linear Landau damping and by filamentation of the most intense laser speckles.The absence of TPD/SRS at higher densities is explained by pump depletion and plasma smoothing driven by filamentation.The prevalence of laser coupling in the low-density profile justifies the low temperature measured for hot electrons(7-12 keV),which is well reproduced by numerical simulations.展开更多
Recently fabricated InSe monolayers exhibit remarkable characteristics that indicate the potential of this material to host a number of many-body phenomena.In this work,we systematically describe collective electronic...Recently fabricated InSe monolayers exhibit remarkable characteristics that indicate the potential of this material to host a number of many-body phenomena.In this work,we systematically describe collective electronic effects in hole-doped InSe monolayers using advanced many-body techniques.To this end,we derive a realistic electronic-structure model from first principles that takes into account the most important characteristics of this material,including a flat band with prominent van Hove singularities in the electronic spectrum,strong electron–phonon coupling,and weakly screened long-ranged Coulomb interactions.We calculate the temperature-dependent phase diagram as a function of band filling and observe that this system is in a regime with coexisting charge density wave and ferromagnetic instabilities that are driven by strong electronic Coulomb correlations.This regime can be achieved at realistic doping levels and high enough temperatures,and can be verified experimentally.We find that the electron–phonon interaction does not play a crucial role in these effects,effectively suppressing the local Coulomb interaction without changing the qualitative physical picture.展开更多
In this work,we investigate collective electronic fluctuations and,in particular,the possibility of the charge density wave ordering in an infinite-layer NdNiO_(2).We perform advanced many-body calculations for the ab...In this work,we investigate collective electronic fluctuations and,in particular,the possibility of the charge density wave ordering in an infinite-layer NdNiO_(2).We perform advanced many-body calculations for the ab-initio three-orbital model by taking into account local correlation effects,nonlocal charge and magnetic fluctuations,and the electron-phonon coupling.We find that in the considered material,electronic correlations are strongly orbital-and momentum-dependent.Notably,the charge density wave and magnetic instabilities originate from distinct orbitals.展开更多
基金support from the Wallenberg Initiative Materials Science for Sustainability (WISE) funded by the Knut and Alice Wallenberg Foundation (KAW) and the European Research Council through the ERC Synergy Grant 854843-FASTCORRO.E. also acknowledges support from STandUPP, eSSENCE, the Swedish Research Council (VR) and the Knut and Alice Wallenberg Foundation (KAW-Scholar program)+1 种基金NL-ECO: Netherlands Initiative for Energy-Efficient Computing (with project number NWA. 1389.20.140) of the NWA research programThe computations/data handling were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) (projects NAISS2024-5-75, NAISS2024-5-427, and NAISS 2024/1-18), partially funded by the Swedish Research Council through grant agreement no. 2022-06725. L.V.P. is thankful to the CPHT computer team for support.
文摘Elemental Pr metal is unique among rare-earth elements in featuring a localized partially filled 4f shell without ordered magnetism.Experimental evidence attributes this absence of magnetismto a singlet crystal-field(CF)ground state of the Pr 4f^(2) configuration.Here,we construct an effective magnetic Hamiltonian for dhcp Pr,by combining density-functional theory with dynamical mean-field theory,in the quasiatomic Hubbard-I approximation.Our calculations fully determine the CF potential and predict singlet CF ground states for both inequivalent Pr sites.The intersite exchange interactions,obtained from the magnetic force theorem,are insufficient to close the CF gap to the magnetic doublets.Hence,ab-initio theory is demonstrated to explain the non-magnetic state of elemental Pr.We also find that the singlet ground state remains robust preventing conventional magnetic orders at the(0001)surface of Pr.Nevertheless,the gap between the ground state and the lowest excited singlet is significantly reduced at the surface,opening the possibility for exotic two-dimensional multipolar orders to emerge within this two-singlet manifold.
基金This work was carried out within the framework of the EUROfusion Consortium,funded by the European Union via the Euratom Research and Training Programme(Grant Agreement No.101052200–EUROfusion)The views and opinions expressed are however those of the author(s)only and do not necessarily reflect those of the European Union or the European Commission.Neither the European Union nor the European Commission can be held responsible for them.The involved teams have operated within the framework of the Enabling Research Project:ENR-IFE.01.CEA‘Advancing shock ignition for direct-drive inertial fusion’This work was also done with the support and under the auspices of the NIFS Collaboration Research program(2021NIFS18KUGK123).
文摘Laser–plasma interaction and hot electrons have been characterized in detail in laser irradiation conditions relevant for direct-drive inertial confinement fusion.The experiment was carried out at the Gekko XII laser facility in multibeam planar target geometry at an intensity of approximately 3×10^(15)W/cm^(2).Experimental data suggest that high-energy electrons,with temperatures of 20–50 keV and conversion efficiencies ofη<1%,were mainly produced by the damping of electron plasma waves driven by two-plasmon decay(TPD).Stimulated Raman scattering(SRS)is observed in a near-threshold growth regime,producing a reflectivity of approximately 0.01%,and is well described by an analytical model accounting for the convective growth in independent speckles.The experiment reveals that both TPD and SRS are collectively driven by multiple beams,resulting in a more vigorous growth than that driven by single-beam laser intensity.
基金We are grateful to E.Baldini,I.Mazin and Yann Gallais for enlightening discussions throughout the course of this work.We would like to thank M.Ye,G.Blumberg,K.Kim,BJ.Kim,MJ.Kim and S.Kaiser for sharing the experimental data of their Raman measurements and valuable discussions.This work is supported by the European Research Council(ERC-2015-AdG-694097)Grupos Consolidados(IT1249-19)+4 种基金the Flatiron Institute,a division of the Simons Foundation.We acknowledge funding by the Deutsche Forschungsgemeinschaft(DFG)under Germany's Excellence Strategy-Cluster of Excellence Advanced Imaging of Matter(AIM)EXC 2056-390715994by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-SFB-925-project 170620586Support by the MaxPlanck Institute-New York City Center for Non-Equilibrium Quantum Phenomena is acknowledgedS.L.acknowledges support from the Alexander von Humboldt foundationG.M.acknowledges support of the Swiss National Science Foundation FNS/SNF through an Ambizione grant.
文摘The structural phase transition in Ta-NiSes has been envisioned as driven by the formation of an excitonic insulating phase.However,the role of structural and electronic instabilities on crystal symmetry breaking has yet to be disentangled.Meanwhile,the phase transition in its complementary material Ta_(2)NiS_(5)does not show any experimental hints of an excitonic insulating phase.We present a microscopic investigation of the electronic and phononic effects involved in the structural phase transition in Ta_(2)NiSe_(5)and Ta-Niss using extensive first-principles calculations.In both materials the crystal symmetries are broken by phonon instabilities,which in tum lead to changes in the electronic bandstructure also observed in the experiment.A total energy landscape analysis shows no tendency towards a purely electronic instability and we find that a sizeable lattice distortion is needed to open a bandgap.We conclude that an excitonic instability is not needed to explain the phase transition in both Ta_(2)NiSe_(5)and Ta_(2)NiS_(5).
基金financial support from the LASERLAB-EUROPE Access to Research Infrastructure activity within the EC’s seventh Framework Program(Application No.18110033)carried out within the framework of the EUROfusion Enabling research projects AWP19-20-ENR-IFE19.CEA01 and AWP21-ENR-01-CEA-02+2 种基金funding from the Euratom research and training programme 20192020 and 2021-2025 under grant No.633053financial support from the CNR-funded Italian research Network ELI-Italy(D.M.No.63108.08.2016)the Czech Ministry of Education,Youth and Sports,project LTT17015。
文摘We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility,aimed at investigating laser±plasma interaction in conditions that are of interest for the shock ignition scheme in inertial confinement fusion(ICF),that is,laser intensity higher than 10^(16) W/cm^(2) impinging on a hot(T>1 keV),inhomogeneous and long scalelength pre-formed plasma.Measurements show a significant stimulated Raman scattering(SRS)backscattering(;%-20%of laser energy)driven at low plasma densities and no signatures of two-plasmon decay(TPD)/SRS driven at the quarter critical density region.Results are satisfactorily reproduced by an analytical model accounting for the convective SRS growth in independent laser speckles,in conditions where the reflectivity is dominated by the contribution from the most intense speckles,where SRS becomes saturated.Analytical and kinetic simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non-linear Landau damping and by filamentation of the most intense laser speckles.The absence of TPD/SRS at higher densities is explained by pump depletion and plasma smoothing driven by filamentation.The prevalence of laser coupling in the low-density profile justifies the low temperature measured for hot electrons(7-12 keV),which is well reproduced by numerical simulations.
基金The work of E.A.S.was supported by the European Union’s Horizon 2020 Research and Innovation programme under the Marie Skłodowska Curie grant agreement No.839551-2DMAGICSThe work of M.I.K.,A.N.R.,and A.I.L.was supported by European Research Council via Synergy Grant 854843-FASTCORR+1 种基金V.H.and A.I.L.acknowledge the support by the Cluster of Excellence“Advanced Imaging of Matter”of the Deutsche Forschungsgemeinschaft(DFG)-EXC 2056-Project No.ID390715994E.A.S.,V.H.,and A.I.L.also acknowledge the support by North-German Supercomputing Alliance(HLRN)under the Project No.hhp00042.
文摘Recently fabricated InSe monolayers exhibit remarkable characteristics that indicate the potential of this material to host a number of many-body phenomena.In this work,we systematically describe collective electronic effects in hole-doped InSe monolayers using advanced many-body techniques.To this end,we derive a realistic electronic-structure model from first principles that takes into account the most important characteristics of this material,including a flat band with prominent van Hove singularities in the electronic spectrum,strong electron–phonon coupling,and weakly screened long-ranged Coulomb interactions.We calculate the temperature-dependent phase diagram as a function of band filling and observe that this system is in a regime with coexisting charge density wave and ferromagnetic instabilities that are driven by strong electronic Coulomb correlations.This regime can be achieved at realistic doping levels and high enough temperatures,and can be verified experimentally.We find that the electron–phonon interaction does not play a crucial role in these effects,effectively suppressing the local Coulomb interaction without changing the qualitative physical picture.
基金the support by the DFG through FOR 5249-449872909(Project P8)and by the European Research Council via Synergy Grant 854843-FASTCORR.
文摘In this work,we investigate collective electronic fluctuations and,in particular,the possibility of the charge density wave ordering in an infinite-layer NdNiO_(2).We perform advanced many-body calculations for the ab-initio three-orbital model by taking into account local correlation effects,nonlocal charge and magnetic fluctuations,and the electron-phonon coupling.We find that in the considered material,electronic correlations are strongly orbital-and momentum-dependent.Notably,the charge density wave and magnetic instabilities originate from distinct orbitals.
