Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electron-phonon coupling and energy flow in a simple metal beyond the
  two-temperature approximation   The electron-phonon coupling and the corresponding energy exchange was
investigated experimentally and by ab initio theory in non-equilibrium states
of the free-electron metal aluminium. The temporal evolution of the atomic mean
squared displacement in laser-excited thin free-standing films was monitored by
femtosecond electron diffraction. The electron-phonon coupling strength was
obtained for a range of electronic and lattice temperatures from density
functional theory molecular dynamics (DFT-MD) simulations. The electron-phonon
coupling parameter extracted from the experimental data in the framework of a
two-temperature model (TTM) deviates significantly from the ab initio values.
We introduce a non-thermal lattice model (NLM) for describing non-thermal
phonon distributions as a sum of thermal distributions of the three phonon
branches. The contributions of individual phonon branches to the
electron-phonon coupling are considered independently and found to be dominated
by longitudinal acoustic phonons. Using all material parameters from
first-principle calculations besides the phonon-phonon coupling strength, the
prediction of the energy transfer from electrons to phonons by the NLM is in
excellent agreement with time-resolved diffraction data. Our results suggest
that the TTM is insufficient for describing the microscopic energy flow even
for simple metals like aluminium and that the determination of the
electron-phonon coupling constant from time-resolved experiments by means of
the TTM leads to incorrect values. In contrast, the NLM describing transient
phonon populations by three parameters appears to be a sufficient model for
quantitatively describing electron-lattice equilibration in aluminium. We
discuss the general applicability of the NLM and provide a criterion for the
suitability of the two-temperature approximation for other metals.

14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an