The Formation of Warm Dense Matter: Experimental Evidence for Electronic Bond Hardening in Gold
Ralph Ernstorfer,*
Maher Harb,
Christoph T. Hebeisen,
Germán Sciaini,
Thibault Dartigalongue,
R. J. Dwayne Miller
Under strong optical excitation conditions, it is possible to
create highly nonequilibrium states of matter. The nuclear response
is determined by the rate of energy transfer from the excited
electrons to the nuclei and the instantaneous effect of change
in electron distribution on the interatomic potential energy
landscape. We used femtosecond electron diffraction to follow
the structural evolution of strongly excited gold under these
transient electronic conditions. Generally, materials become
softer with excitation. In contrast, the rate of disordering
of the gold lattice is found to be retarded at excitation levels
up to 2.85 megajoules per kilogram with respect to the degree
of lattice heating, which is indicative of increased lattice
stability at high effective electronic temperatures, a predicted
effect that illustrates the strong correlation between electronic
structure and lattice bonding.
* Present address: Physik Department E11, Technische Universität München, D-85747 Garching, Germany.
To whom correspondence should be addressed. E-mail: dmiller{at}lphys.chem.utoronto.ca
