Free electron laser-driven ultrafast rearrangement of the electronic structure in Ti

Principi, Emiliano; Giangrisostomi, Erika; Cucini, Riccardo; Bencivenga, Filippo; Battistoni, Andrea; Gessini, Alessandro; Mincigrucci, Riccardo; Saito, Makina; Fonzo, S. Di; D’Amico, Francesco; Cicco, Andrea Di; Gunnella, R.; Filipponi, A.; Giglia, Angelo; Nannarone, Stefano; Masciovecchio, C.

doi:10.1063/1.4935687

Cited by 13 publications

(9 citation statements)

References 28 publications

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“…8000 ± 800 1410 ± 30 9.8 10.0 0.10 5 × 10 12 18 600 ± 1400 5200 ± 100 13.0 9.7 0.14 1 × 10 13 20 100 ± 300 4900 ± 300 12.2 9.2 0.59 Ni as discussed above. At higher laser intensity, when such excitation becomes possible the fraction of sp electrons also increases as in the case of Ni.…”

Section: Sp Band Vs D Band Thermalization Of Partially Filled D-bamentioning

confidence: 83%

“…As a result, the electron temperature stays above the lattice temperature during several picoseconds and the framework of a two-temperature model (TTM) can be used to describe laser-induced processes in metals [10,11]. Beyond a standard TTM, a fast electron thermalization is also assumed to describe the effect of high electron temperature on electronic, optical and thermal properties of metals [12][13][14][15][16]. The modification of electronic structure due to increase of the effective electron temperature can change the metal melting temperature [17,18], induce solid-solid phase transformation [19][20][21][22], and affect electron-phonon coupling dynamics [23,24].…”

Section: Introductionmentioning

confidence: 99%

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Ultrafast electron dynamics and orbital-dependent thermalization in photoexcited metals

et al. 2018

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We use a time-dependent density functional theory (TDDFT) to analyze nonequilibrium dynamics of laserexcited electrons in transition metals (Ni, Cr, Cu) and shed light on the ultrafast thermalization process from a microscopical point of view. As a first result, after instant increase of the electron temperature up to 50 000 K, we observe that the dynamics of electron density of states is faster than a laser subcycle, on the attosecond timescale. This is related to an ultrafast rearrangement of excited electrons in space to accommodate strong changes in ion screening. Secondly, we show that the electron thermalization dynamics strongly depends on the electronic structure of a given metal. Excited by a 7-fs laser pulse, d-block transition metals exhibit two subsystems of electrons, each one achieving its own temperature. Due to a higher localization, electrons from d block stay cold, while excited delocalized sp electrons rapidly reach a high temperature. Electrons of each band of energy are mutually thermalized within the time of the laser pulse. Much more time is however needed to reach equilibrium of the whole electronic system. These results redraw the validity limits of current two-temperature models during the laser irradiation time, potentially impacting further material reaction.

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Section: Sp Band Vs D Band Thermalization Of Partially Filled D-bamentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Ultrafast electron dynamics and orbital-dependent thermalization in photoexcited metals

et al. 2018

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“…This approximation is based on efficient screening of the optical field by surface electrons 21 and space-charge limitation of the maximum optical field intensity 22 . In contrast, femto-and picosecond core-level photoabsorption of metals systematically shows signatures of excitation-induced electronic structure modification at high intensities [23][24][25][26] . To bridge this gap of intensities and timescales, we used attosecond transient absorption spectroscopy to study collective electron dynamics in the transition metals Ti and Zr.…”

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confidence: 92%

Attosecond screening dynamics mediated by electron localization in transition metals

et al. 2019

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Transition metals with their densely confined and strongly coupled valence electrons are key constituents of many materials with unconventional properties 1 , such as high-Tc superconductors, Mott insulators and transition-metal dichalcogenides 2 . Strong electron interaction offers a fast and efficient lever to manipulate their properties with light, creating promising potential for next-generation electronics 3-6 . However, the underlying dynamics is a fast and intricate interplay of polarization and screening effects, which is poorly understood. It is hidden below the femtosecond timescale of electronic thermalization, which follows the light-induced excitation 7 . Here, we investigate the many-body electron dynamics in transition metals before thermalization sets in. We combine the sensitivity of intra-shell transitions to screening effects 8 with attosecond time resolution to uncover the interplay of photo-absorption and screening. First-principles time-dependent calculations allow us to assign our experimental observations to ultrafast electronic localization on d-orbitals. The latter modifies the whole electronic structure as well as the collective dynamic response of the system on a timescale much faster than the light-field cycle. Our results demonstrate a possibility for steering the electronic properties of solids prior to electron thermalization, suggesting that the ultimate speed of electronic phase transitions is limited only by the duration of the controlling laser pulse. Furthermore, external control of the local electronic density serves as a fine tool for testing state-of-the art models of electron-electron interactions. We anticipate our study to facilitate further investigations of electronic phase transitions, laser-metal interactions and photo-absorption in correlated electron systems on its natural timescale.A characteristic thermalization time of laser-excited hot electrons in solids is in the femtosecond regime and becomes faster with stronger electron interactions 7 . Therefore, attosecond time resolution is required to resolve coupled electron dynamics during the lasermatter interaction before electron thermalization has occurred. Attosecond transient absorption spectroscopy revealed electric-field-guided electron dynamics in simple dielectrics and semiconductors 9-14 . However, transient absorption studies of localized and strongly interacting electrons, such as on d-and f-orbitals of transition metals, have been limited to the fewfemtosecond regime 15 . Transition metal elements are the key constituents of many materials exhibiting remarkable properties, such as Mott insulators, high-Tc superconductors and transition metal dichalcogenides 2 . Understanding the coupled-electron dynamics in these systems is central for their applications in optoelectronics, energy-efficient electronics, magnetic-memory devices, spintronics and new solar cells 16 . Transition metal elements were studied with attosecond photoemission spectroscopy [17][18][19] . However, state-of-the-art theoretical

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“…Examples of pioneering soft X-ray L-edge FEL-XAS transmission experiments include measurements of Al, Ge and Ti thin films for variable fluence (see, for example, [37][38][39]). In those experiments, ultrafast electron heating pumping matter at extremely high temperatures, as well as saturable absorption effects were observed.…”

Section: Time-resolved X-ray Absorption Spectroscopy In the Water Windowmentioning

confidence: 99%

“…Another field where one can exploit the XUV photons generated by the EuPRAXIA@SPARC_LAB FEL is the study by means of coherent electronic Raman process [39] of photo-induced chemical processes represented by the detection of electronic coherences (based on a composite X-ray pulse sequence) generated during the system dynamics [60]. For example, within such a scheme, a combination of short, soft X-ray FEL pulses can be used to directly detect the passage through conical intersections (CIs).…”

Section: Time-resolved Coherent Raman Experiments With X-ray Pulsesmentioning

confidence: 99%

The Potential of EuPRAXIA@SPARC_LAB for Radiation Based Techniques

et al. 2019

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A proposal for building a Free Electron Laser, EuPRAXIA@SPARC_LAB, at the Laboratori Nazionali di Frascati, is at present under consideration. This FEL facility will provide a unique combination of a high brightness GeV-range electron beam generated in a X-band RF linac, a 0.5 PW-class laser system and the first FEL source driven by a plasma accelerator. The FEL will produce ultra-bright pulses, with up to 10 12 photons/pulse, femtosecond timescale and wavelength down to 3 nm, which lies in the so called “water window”. The experimental activity will be focused on the realization of a plasma driven short wavelength FEL able to provide high-quality photons for a user beamline. In this paper, we describe the main classes of experiments that will be performed at the facility, including coherent diffraction imaging, soft X-ray absorption spectroscopy, Raman spectroscopy, Resonant Inelastic X-ray Scattering and photofragmentation measurements. These techniques will allow studying a variety of samples, both biological and inorganic, providing information about their structure and dynamical behavior. In this context, the possibility of inducing changes in samples via pump pulses leading to the stimulation of chemical reactions or the generation of coherent excitations would tremendously benefit from pulses in the soft X-ray region. High power synchronized optical lasers and a TeraHertz radiation source will indeed be made available for THz and pump–probe experiments and a split-and-delay station will allow performing XUV-XUV pump–probe experiments.

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Free electron laser-driven ultrafast rearrangement of the electronic structure in Ti

Cited by 13 publications

References 28 publications

Ultrafast electron dynamics and orbital-dependent thermalization in photoexcited metals

Ultrafast electron dynamics and orbital-dependent thermalization in photoexcited metals

Attosecond screening dynamics mediated by electron localization in transition metals

The Potential of EuPRAXIA@SPARC_LAB for Radiation Based Techniques

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