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Title: Langevin Dynamics with Spatial Correlations as a Model for Electron-Phonon Coupling

Stochastic Langevin dynamics has been traditionally used as a tool to describe nonequilibrium processes. When utilized in systems with collective modes, traditional Langevin dynamics relaxes all modes indiscriminately, regardless of their wavelength. In this paper, we propose a generalization of Langevin dynamics that can capture a differential coupling between collective modes and the bath, by introducing spatial correlations in the random forces. This allows modeling the electronic subsystem in a metal as a generalized Langevin bath endowed with a concept of locality, greatly improving the capabilities of the two-temperature model. The specific form proposed here for the spatial correlations produces a physical wave-vector and polarization dependency of the relaxation produced by the electron-phonon coupling in a solid. We show that the resulting model can be used for describing the path to equilibration of ions and electrons and also as a thermostat to sample the equilibrium canonical ensemble. By extension, the family of models presented here can be applied in general to any dense system, solids, alloys, and dense plasmas. Finally, as an example, we apply the model to study the nonequilibrium dynamics of an electron-ion two-temperature Ni crystal.
Authors:
 [1] ;  [2] ;  [3] ; ORCiD logo [4] ;  [5] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Quantum Simulations Group
  2. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Arlington, VA (United States). Dept. of Mechanical Engineering
  3. George Washington Univ., Ashburn, VA (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  5. Uppsala Univ. (Sweden). Dept. of Physics and Astronomy
Publication Date:
Report Number(s):
LLNL-JRNL-743460
Journal ID: ISSN 0031-9007; 898486
Grant/Contract Number:
AC52-07NA27344; AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 120; Journal Issue: 18; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; electron-phonon coupling; phonons; Langevin equation; molecular dynamics
OSTI Identifier:
1458684
Alternate Identifier(s):
OSTI ID: 1436003; OSTI ID: 1459271

Tamm, Artur, Caro, Magdalena, Caro, Alfredo, Samolyuk, German D., Klintenberg, Mattias, and Correa, Alfredo A.. Langevin Dynamics with Spatial Correlations as a Model for Electron-Phonon Coupling. United States: N. p., Web. doi:10.1103/PhysRevLett.120.185501.
Tamm, Artur, Caro, Magdalena, Caro, Alfredo, Samolyuk, German D., Klintenberg, Mattias, & Correa, Alfredo A.. Langevin Dynamics with Spatial Correlations as a Model for Electron-Phonon Coupling. United States. doi:10.1103/PhysRevLett.120.185501.
Tamm, Artur, Caro, Magdalena, Caro, Alfredo, Samolyuk, German D., Klintenberg, Mattias, and Correa, Alfredo A.. 2018. "Langevin Dynamics with Spatial Correlations as a Model for Electron-Phonon Coupling". United States. doi:10.1103/PhysRevLett.120.185501.
@article{osti_1458684,
title = {Langevin Dynamics with Spatial Correlations as a Model for Electron-Phonon Coupling},
author = {Tamm, Artur and Caro, Magdalena and Caro, Alfredo and Samolyuk, German D. and Klintenberg, Mattias and Correa, Alfredo A.},
abstractNote = {Stochastic Langevin dynamics has been traditionally used as a tool to describe nonequilibrium processes. When utilized in systems with collective modes, traditional Langevin dynamics relaxes all modes indiscriminately, regardless of their wavelength. In this paper, we propose a generalization of Langevin dynamics that can capture a differential coupling between collective modes and the bath, by introducing spatial correlations in the random forces. This allows modeling the electronic subsystem in a metal as a generalized Langevin bath endowed with a concept of locality, greatly improving the capabilities of the two-temperature model. The specific form proposed here for the spatial correlations produces a physical wave-vector and polarization dependency of the relaxation produced by the electron-phonon coupling in a solid. We show that the resulting model can be used for describing the path to equilibration of ions and electrons and also as a thermostat to sample the equilibrium canonical ensemble. By extension, the family of models presented here can be applied in general to any dense system, solids, alloys, and dense plasmas. Finally, as an example, we apply the model to study the nonequilibrium dynamics of an electron-ion two-temperature Ni crystal.},
doi = {10.1103/PhysRevLett.120.185501},
journal = {Physical Review Letters},
number = 18,
volume = 120,
place = {United States},
year = {2018},
month = {5}
}