Ultrafast Heating Induced Suppression of d-band Dominance in the Electronic Excitation Spectrum of Cuprum
arxiv(2024)
摘要
The combination of isochoric heating of solids by free electron lasers (FEL)
and in situ diagnostics by X-ray Thomson scattering (XRTS) allows for
measurements of material properties at warm dense matter (WDM) conditions
relevant for astrophysics, inertial confinement fusion, and material science.
In the case of metals, the FEL beam pumps energy directly into electrons with
the lattice structure of ions being nearly unaffected. This leads to a unique
transient state that gives rise to a set of interesting physical effects, which
can serve as a reliable testing platform for WDM theories. In this work, we
present extensive linear-response time-dependent density functional theory
(TDDFT) results for the electronic dynamic structure factor of isochorically
heated copper with a face-centered cubic lattice. At ambient conditions, the
plasmon is heavily damped due to the presence of d-band excitations, and its
position is independent of the wavenumber. In contrast, the plasmon feature
starts to dominate the excitation spectrum and has a Bohm-Gross type plasmon
dispersion for temperatures T ≥ 4 eV, where the quasi-free electrons
in the interstitial region are in the WDM regime. In addition, we analyze the
thermal changes in the d-band excitations and outline the possibility to use
future XRTS measurements of isochorically heated copper as a controlled testbed
for WDM theories.
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