Ultra-fast dynamics in solids: non-equilibrium behaviour of magnetism and atomic structure

Bennemann, K.H.

doi:10.1002/andp.200810354

Cited by 12 publications

(13 citation statements)

References 58 publications

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“…In the extreme case the energy barrier between the two phases involved is canceled, which triggers a pure nonthermal phase transition on the sub-ps time scale. Theory 32 and experiments 33 have shown that the driving parameter in this type of transition is the free-electron density. A minimum value of around 10% of the valence band electrons is required for a nonthermal process to occur.…”

Section: Discussionmentioning

confidence: 99%

Amorphous to crystalline phase transition in carbon induced by intense femtosecond x-ray free-electron laser pulses

Gaudin¹,

Peyrusse²,

Chalupský³

et al. 2012

Phys. Rev. B

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We present the results of an experiment where amorphous carbon undergoes a phase transition induced by femtosecond 830 eV x-ray free-electron laser pulses. The phase transition threshold fluence is found to be 282 ± 11 mJ/cm 2 . Atomic force microscopy, photoelectron microscopy, and micro-Raman spectroscopy give experimental evidence for the phase transition in terms of a volume expansion, graphitization, and change of local order of the irradiated sample area. The interaction is modeled by an accurate time-dependent treatment of the ionization dynamics coupled to a two-temperature model. At the phase transition fluence threshold the free-electron density N e is found to be at maximum 9 × 10 20 cm −3 while the ion (atom) temperature is found to be 1050 K, e.g., above the crystallization activation temperature reported in the literature. This low ionization rate and high atom temperature suggest a thermally activated phase transition.

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Section: Discussionmentioning

confidence: 99%

Amorphous to crystalline phase transition in carbon induced by intense femtosecond x-ray free-electron laser pulses

Gaudin¹,

Peyrusse²,

Chalupský³

et al. 2012

Phys. Rev. B

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“…(1) and (2). Finally, we neglect the blast force 16 resulting from the gradient of electronic temperature as we assume homogeneous excitations.…”

Section: Description Of Electronic Subsystemmentioning

confidence: 99%

“…[1][2][3][4][5][6] In this context, metals are often used as a playground to study the dynamics of an excited electron gas. The fast and complex nuclear dynamics following electronic excitation can now be probed more directly by ultrafast electron diffraction (UED) and time-resolved x-ray diffraction (tr-XD).…”

Section: Introductionmentioning

confidence: 99%

Structural dynamics of laser-irradiated gold nanofilms

et al. 2013

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We performed relativistic ultrafast electron diffraction (UED) measurements of the structural dynamics of photoexcited gold nanofilms and developed an atomistic model, based on the two-temperature molecular dynamics (2T-MD) method, which allows us to make a direct comparison of the time evolutions of measured and calculated Bragg peaks. The quantitative agreement between the temporal evolutions of the experimental and theoretical Bragg peaks at all fluences suggests that the 2T-MD method provides a faithful atomistic representation of the structural evolution of photoexcited gold films. The results reveal the transition between slow heterogeneous melting at low absorbed photon fluence to rapid homogeneous melting at higher fluence and nonthermally driven melting at very high fluence. At high laser fluence, the time evolution of Bragg peaks calculated using the conventional 2T-MD model disagrees with experiment. We show that using an interatomic potential that directly depends on the electron temperature delivers a much better agreement with UED data. Finally, our ab initio calculations of phonon spectra suggest electronic bond softening, if the nanofilms can expand freely under electronic pressure, and bond hardening, if they are constrained in all three dimensions.

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“…Electronic excitation of a solid by femtosecond laser pulses can create a transient nonequilibrium state in which the electron subsystem is "hot" and the ion subsystem remains close to its initial temperature [1,2]. Such excitation modifies the electron density distribution in a solid giving rise to modified forces between atoms.…”

Section: Introductionmentioning

confidence: 99%

Nonthermal solid-to-solid phase transitions in tungsten

et al. 2014

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The ab initio calculations of phonon dispersions and nonthermal forces along structural deformation paths were used to study nonthermal solid-to-solid phase transitions in photoexcited tungsten. We assumed that electronic excitation can be described by an electronic temperature and demonstrated that nonthermal, i.e., caused purely by electronic excitation, bcc-to-fcc and bcc-to-hcp phase transitions can occur for electronic temperatures between 1.7 and 4.3 eV. These transitions result from soft modes along the line of the Brillouin zone. Structural path calculations at different electronic temperatures indicate that both transitions are likely to take place in nonequilibrium conditions. We further predict that transient fcc and hcp phases of tungsten could be observed for several ps.

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Ultra-fast dynamics in solids: non-equilibrium behaviour of magnetism and atomic structure

Cited by 12 publications

References 58 publications

Amorphous to crystalline phase transition in carbon induced by intense femtosecond x-ray free-electron laser pulses

Amorphous to crystalline phase transition in carbon induced by intense femtosecond x-ray free-electron laser pulses

Structural dynamics of laser-irradiated gold nanofilms

Nonthermal solid-to-solid phase transitions in tungsten

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