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Effect of spin-orbit coupling on the high harmonics from the topological Dirac semimetal Na3Bi

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npj Computational Materials 2022年第1期8卷 1379-1387页

作者： Nicolas Tancogne-Dejean Florian G.Eich angel rubio Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science Luruper Chaussee 14922761HamburgGermany European Theoretical Spectroscopy Facility(ETSF) Donostia-San SebastianSpain HQS Quantum Simulations GmbH Haid-und-Neu-Straße 7D-76131KarlsruheGermany Nano-Bio Spectroscopy Group Universidad del País Vasco20018San SebastiánSpain Center for Computational Quantum Physics(CCQ) The Flatiron Institute162 Fifth AvenueNew YorkNY10010USA

In this work,we performed extensive first-principles simulations of high-harmonic generation in the topological Diract semimetal Na_(3)Bi using a first-principles time-dependent density functional theory framework,focusing on the effect of spin-orbit coupling(SOC)on the harmonic *** also derived an analytical model describing the microscopic mechanism of strong-field dynamics in presence of spin-orbit coupling,starting from a locally U(1)×SU(2)gauge-invariant *** results reveal that SOC:(i)affects the strong-field excitation of carriers to the conduction bands by modifying the bandstructure of Na_(3)Bi,(ii)makes each spin channel reacts differently to the driven laser by modifying the electron velocity(iii)changes the emission timing of the emitted ***,we show that the SOC affects the harmonic emission by directly coupling the charge current to the spin currents,paving the way to the high-harmonic spectroscopy of spin currents in solids.

关键词： coupling harmonic harmonics

Controlling the magnetic state of the proximate quantum spin liquid α-RuCl_(3) with an optical cavity

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npj Computational Materials 2023年第1期9卷 265-274页

作者： Emil Viñas Boström Adithya Sriram Martin Claassen angel rubio Max Planck Institute for the Structure and Dynamics of Matter Luruper Chaussee 14922761 HamburgGermany Department of Physics Stanford UniversityStanfordCA 94305USA Department of Physics and Astronomy University of PennsylvaniaPhiladelphiaPA 19104USA Center for Computational Quantum Physics Flatiron InstituteSimons FoundationNew York CityNY 10010USA

Harnessing the enhanced light-matter coupling and quantum vacuum fluctuations resulting from mode volume compression in optical cavities is a promising route towards functionalizing quantum materials and realizing exotic states of ***,we extend cavity quantum electrodynamical materials engineering to correlated magnetic systems,by demonstrating that a Fabry-Pérot cavity can be used to control the magnetic state of the proximate quantum spin liquidα-RuCl_(3).Depending on specific cavity properties such as the mode frequency,photon occupation,and strength of the light-matter coupling,any of the magnetic phases supported by the extended Kitaev model can be *** particular,in the THz regime,we show that the cavity vacuum fluctuations alone are sufficient to bringα-RuCl_(3) from a zigzag antiferromagnetic to a ferromagnetic *** external pumping of the cavity in the few photon limit,it is further possible to push the system into the antiferromagnetic Kitaev quantum spin liquid state.

关键词： state quantum magnetic

Optimal thermoelectric figure of merit of Si/Ge core-shell nanowires

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Nano Research 2015年第8期8卷 2611-2619页

作者： Kaike Yang Andres Cantarero angel rubio Roberto D'Agosta Nano-Bio Spectroscopy Group and ETSF Scientific Development Center Departamento de Fisica de Materiales Universidad del Pais Vasco UPV/EHU San Sebastian 20018 Spain Instituto de Ciencia de Materiales Universidad de Valencia Valencia 46071 Spain Ikerbasque Basque foundation for Science Bilbao 48013 Spain

We investigate the thermoelectric energy conversion efficiency of Si and Ge nanowires, and in particular, that of Si/Ge core-shell nanowires. We show how the presence of a thin Ge shell on a Si core nanowire increases the overall figure of merit. We find the optimal thickness of the Ge shell to provide the largest figure of merit for the devices. We also consider Ge core/Si shell nanowires, and show that an optimal thickness of the Si shell does not exist, since the figure of merit is a monotonically decreasing function of the radius of the nanowire. Finally, we verify the empirical law relating the electron energy gap to the optimal working temperature that maximizes the efficiency of the device.

关键词： thermoelectric properties Seebeck coefficient silicon and germanium core-shell nanowires

Attosecond magnetization dynamics in non-magnetic materials driven by intense femtosecond lasers

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npj Computational Materials 2023年第1期9卷 1959-1968页

作者： Ofer Neufeld Nicolas Tancogne-Dejean Umberto De Giovannini Hannes Hübener angel rubio Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science Hamburg 22761Germany Universitàdegli Studi di Palermo Dipartimento di Fisica e Chimica—Emilio SegrèPalermo I-90123Italy Center for Computational Quantum Physics(CCQ) The Flatiron InstituteNew YorkNY 10010USA

Irradiating solids with ultrashort laser pulses is known to initiate femtosecond timescale magnetization ***,sub-femtosecond spin dynamics have not yet been observed or ***,we explore ultrafast light-driven spin dynamics in a highly nonresonant strong-field *** state-of-the-art ab initio calculations,we predict that a nonmagnetic material can transiently transform into a magnetic one via dynamical extremely nonlinear spin-flipping processes,which occur on attosecond timescales and are mediated by cascaded multi-photon and spin–orbit *** are nonperturbative nonresonant analogs to the inverse Faraday effect,allowing the magnetization to evolve in very high harmonics of the laser frequency(*** up to the 42nd,oscillating at~100 attoseconds),and providing control over the speed of magnetization by tuning the laser power and ***,we show that even for linearly polarized driving,where one does not intuitively expect the onset of an induced magnetization,the magnetization transiently oscillates as the system interacts with *** response is enabled by transverse light-driven currents in the solid,and typically occurs on timescales of~500 attoseconds(with the slower femtosecond response suppressed).An experimental setup capable of measuring these dynamics through pump–probe transient absorption spectroscopy is *** results pave the way for attosecond regimes of manipulation of magnetism.

关键词： tuning transient dynamics

High-harmonic generation from spin-polarised defects in solids

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npj Computational Materials 2020年第1期6卷 1583-1591页

作者： M.S.Mrudul Nicolas Tancogne-Dejean angel rubio Gopal Dixit Department of Physics Indian Institute of Technology BombayPowaiMumbai 400076India Max Planck Institute for the Structure and Dynamics of Matter Luruper Chaussee 14922761 HamburgGermany Nano-Bio Spectroscopy Group and ETSF Departamento de Fisica de MaterialesUniversidad del País Vasco UPV/EHU20018 San SebastiánSpain

The generation of high-order harmonics in gases enabled to probe the attosecond electron dynamics in atoms and molecules with unprecedented *** these techniques to solids,which were originally developed for atomic and molecular gases,requires a fundamental understanding of the physics that has been partially addressed ***,we employ timedependent density-functional theory to investigate how the electron dynamics resulting in high-harmonic emission in monolayer hexagonal boron nitride is affected by the presence of *** show how these realistic spin-polarised defects modify the harmonic emission and demonstrate that important differences exist between harmonics from a pristine solid and a defected *** particular,we found that the different spin channels are affected differently by the presence of the spin-polarised point ***,the localisation of the wavefunction,the geometry of the defect,and the electron–electron interaction are all crucial ingredients to describe high-harmonic generation in defected solids.

关键词： harmonic solids harmonics

Orbital magneto-optical response of periodic insulators from first principles

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npj Computational Materials 2019年第1期5卷 874-882页

作者： Irina V.Lebedeva David A.Strubbe Ilya V.Tokatly angel rubio Nano-Bio Spectroscopy Group and ETSF Departamento de Física de MaterialesUniversidad del País Vasco UPV/EHU20018 San SebastiánSpain Department of Physics School of Natural SciencesUniversity of CaliforniaMercedCA 95343USA Donostia International Physics Center(DIPC) Manuel de Lardizabal 520018 San SebastiánSpain IKERBASQUE Basque Foundation for Science48011 BilbaoSpain Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science Luruper Chaussee 14922761 HamburgGermany

Magneto-optical response,*** response in the presence of a magnetic field,is commonly used for characterization of materials and in optical ***,quantum mechanical description of electric and magnetic fields in crystals is not straightforward as the position operator is ill *** present a reformulation of the density matrix perturbation theory for time-dependent electromagnetic fields under periodic boundary conditions,which allows us to treat the orbital magneto-optical response of solids at the ab initio *** efficiency of the computational scheme proposed is comparable to standard linearresponse calculations of absorption spectra and the results of tests for molecules and solids agree with the available experimental data.A clear signature of the valley Zeeman effect is revealed in the continuum magneto-optical spectrum of a single layer of hexagonal boron *** present formalism opens the path towards the study of magneto-optical effects in strongly driven low-dimensional systems.

关键词： periodic magneto solids

Dynamical amplification of electric polarization through nonlinear phononics in 2D SnTe

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npj Computational Materials 2020年第1期6卷 155-162页

作者： Dongbin Shin Shunsuke A.Sato Hannes Hübener Umberto De Giovannini Noejung Park angel rubio Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science Luruper Chaussee 149Hamburg 22761Germany Center for Computational Sciences University of TsukubaTsukuba 305-8577Japan Nano-Bio Spectroscopy Group Departamento de Fisica de MaterialesUniversidad del Pas VascoSan Sebastian 20018Spain Department of Physics Ulsan National Institute of Science and TechnologyUNIST-gil 50Ulsan 44919Korea Center for Computational Quantum Physics(CCQ) The Flatiron Institute162 Fifth AvenueNew YorkNY 10010USA

Ultrafast optical control of ferroelectricity using intense terahertz fields has attracted significant *** we show that the nonlinear interactions between two optical phonons in SnTe,a two-dimensional in-plane ferroelectric material,enables a dynamical amplification of the electric polarization within subpicoseconds time *** first-principles time-dependent simulations show that the infrared-active out-of-plane phonon mode,pumped to nonlinear regimes,spontaneously generates in-plane motions,leading to rectified oscillations in the in-plane electric *** suggest that this dynamical control of ferroelectric material,by nonlinear phonon excitation,can be utilized to achieve ultrafast control of the photovoltaic or other nonlinear optical responses.

关键词： nonlinear ferroelectric phonon

Common microscopic origin of the phase transitions in Ta_(2)NiS_(5) and the excitonic insulator candidate Ta_(2)NiSe_(5)

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npj Computational Materials 2021年第1期7卷 1919-1932页

作者： Lukas Windgätter Malte Rösner Giacomo Mazza Hannes Hübener Antoine Georges Andrew J.Millis Simone Latini angel rubio Max Planck Institute for the Structure and Dynamics of Matter Luruper Chaussee 14922761 HamburgGemany Radboud University Institute for Molecules and MaterialsHeijendaalseweg 1356525 AJ NijmegenNetherlands Department of Quantum Matter Physics University of GenevaQuai Ernest-Ansermet 241211 GenevaSwitzerland College de France 11 place Marcelin Berthelot75005 ParisFrance Center for Computational Quantum Physics Flatiron InstituteNew YorkNY 10010USA.CPHTCNRSEcole PolytechniqueIP Paris91128 PalaiseauFrance Department of Physics Columbia UniversityNew YorkNY 10027USA.Nano-Bio Spectroscopy Group Departamento de Fisica de Materiales Universidad del Pais Vasco20018 San SebastianSpain

The structural phase transition in Ta-NiSes has been envisioned as driven by the formation of an excitonic insulating ***,the role of structural and electronic instabilities on crystal symmetry breaking has yet to be ***,the phase transition in its complementary material Ta_(2)NiS_(5)does not show any experimental hints of an excitonic insulating *** 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 *** 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 *** conclude that an excitonic instability is not needed to explain the phase transition in both Ta_(2)NiSe_(5)and Ta_(2)NiS_(5).

关键词： phase structural transitions

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进行中的弗洛凯能带工程

Science Bulletin 2023年第8期68卷 751-752页

作者： Hannes Hübener Umberto De Giovannini Shunsuke A.Sato angel rubio Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science Hamburg 22761Germany Universitàdegli Studi di Palermo Dipartimento di Fisica e Chimica—Emilio SegrèPalermo I-90123Italy Center for Computational Sciences University of TsukubaTsukuba 305-8577Japan Center for Computational Quantum Physics(CCQ) The Flatiron InstituteNew York NY 10010USA

In a recent article in Nature,Zhou et al.[1]reported an impressive demonstration of Floquet materials *** this field researchers aim at creating properties in materials that they do not usually exhibit in their equilibrium *** scope ranges from inducing phase transitions in out-of-equilibrium that can otherwise only be achieved by pressure or doping.

关键词：能带工程 equilibrium otherwise