Signatures of nonthermal melting

Zier, Tobias; Zijlstra, Eeuwe S.; Kalitsov, Alan; Theodonis, Ioannis; Garcia, Martín E.

doi:10.1063/1.4928686

Cited by 32 publications

(30 citation statements)

References 35 publications

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“…Most ab initio studies of nonthermal melting in silicon have been built on two assumptions: thermalized electrons and the BornOppenheimer approximation, which excludes nonadiabatic effects such as electron-phonon coupling, e.g., Refs. [16][17][18][19][20][21][22]. These studies do predict bond softening at high excitations but they predict melting to occur at higher excitations than expected based on experiment.…”

Section: Introductionmentioning

confidence: 85%

“…Silicon is a widely studied material in the context of strongly driven phase transitions, both experimentally [1][2][3][4][5][6] and theoretically [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], where it is found to melt on a subpicosecond timescale at high excitations. Most theoretical studies of nonthermal melting in silicon have employed ab initio simulation methods.…”

Section: Introductionmentioning

confidence: 99%

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Simulating electronically driven structural changes in silicon with two-temperature molecular dynamics

Darkins

Murphy

et al. 2018

Phys. Rev. B

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Radiation can drive the electrons in a material out of thermal equilibrium with the nuclei, producing hot, transient electronic states that modify the interatomic potential energy surface. We present a rigorous formulation of two-temperature molecular dynamics that can accommodate these electronic effects in the form of electronic-temperature-dependent force fields. Such a force field is presented for silicon, which has been constructed to reproduce the ab initio-derived thermodynamics of the diamond phase for electronic temperatures up to 2.5 eV, as well as the structural dynamics observed experimentally under nonequilibrium conditions in the femtosecond regime. This includes nonthermal melting on a subpicosecond timescale to a liquidlike state for electronic temperatures above ∼1 eV. The methods presented in this paper lay a rigorous foundation for the large-scale atomistic modeling of electronically driven structural dynamics with potential applications spanning the entire domain of radiation damage.

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Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Simulating electronically driven structural changes in silicon with two-temperature molecular dynamics

Darkins

Murphy

et al. 2018

Phys. Rev. B

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show abstract

“…Our MTM shows that certain phonon temperatures can be much higher than the apparent lattice temperature. These hot phonons can displace the lattice along their eigenvectors and result in "nonthermal damage" of the device even though the apparent temperature is still lower than the damage threshold [54,55]. Therefore, MTM is advantageous over TTM for thermal design to better prevent such nonthermal device failures.…”

Section: B a Comparison With The Original Two-temperature Modelmentioning

confidence: 99%

Phonon branch-resolved electron-phonon coupling and the multitemperature model

Vallabhaneni

Cao

et al. 2018

Phys. Rev. B

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Electron-phonon (e-p) interaction and transport are important for laser-matter interactions, hot-electron relaxation, and metal-nonmetal interfacial thermal transport. A widely used approach is the two-temperature model (TTM), where e-p coupling is treated with a gray approach with a lumped coupling factor G ep and the assumption that all phonons are in local thermal equilibrium. However, in many applications, different phonon branches can be driven into strong nonequilibrium due to selective e-p coupling, and a TTM analysis can lead to misleading or wrong results. Here, we extend the original TTM into a general multitemperature model (MTM), by using phonon branch-resolved e-p coupling factors and assigning a separate temperature for each phonon branch. The steady-state thermal transport and transient hot electron relaxation processes in constant and pulse laser-irradiated single-layer graphene (SLG) are investigated using our MTM respectively. Results show that different phonon branches are in strong nonequilibrium, with the largest temperature rise being more than six times larger than the smallest one. A comparison with TTM reveals that under steady state, MTM predicts 50% and 80% higher temperature rises for electrons and phonons respectively, due to the "hot phonon bottleneck" effect. Further analysis shows that MTM will increase the predicted thermal conductivity of SLG by 67% and its hot electron relaxation time by 60 times. We expect that our MTM will prove advantageous over TTM and gain use among experimentalists and engineers to predict or explain a wide ranges of processes involving laser-matter interactions.

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“…This process is known as nonthermal melting. [63][64][65] However, the latter occurs only upon femtosecond excitation at a laser uency of about 0.2 J cm À2 .…”

Section: Papermentioning

confidence: 99%

Laser-flash-photolysis-spectroscopy: a nondestructive method?

et al. 2017

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Herein, we report the effect of the laser illumination during the diffuse-reflectance laser-flash-photolysis measurements on the morphological and optical properties of TiO powders. A grey-blue coloration of the TiO nanoparticles has been observed after intense laser illumination. This is explained by the formation of nonreactive trapped electrons accompanied by the release of oxygen atoms from the TiO matrix as detected by means of UV-vis and EPR spectroscopy. Moreover, in the case of the pure anatase sample a phase transition of some TiO nanoparticles located in the inner region from anatase to rutile occurred. It is suggested that these structural changes in TiO are caused by an energy and charge transfer to the TiO lattice.

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Signatures of nonthermal melting

Cited by 32 publications

References 35 publications

Simulating electronically driven structural changes in silicon with two-temperature molecular dynamics

Simulating electronically driven structural changes in silicon with two-temperature molecular dynamics

Phonon branch-resolved electron-phonon coupling and the multitemperature model

Laser-flash-photolysis-spectroscopy: a nondestructive method?

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