Observation of a nonthermal disordered lattice state in heat-induced structural phase change in gold

Summary form only given. Although structural phase change in metals is a vital problem due to its fundamental importance as well as wide applicability in materials processing and manufacturing, the underlying physics of this process is still not fully understood. Recently, we demonstrated pronounced electronic effects in structural phase changes in rnetals induced by both electronic excitation and conventional thermal heating. The observed electronic effects in conventional heat-induced structural change, however, become clear only in a relatively long time scale (a few ps after laser excitation) when phonons become highly excited. It is fundamentally important to understand electronic effects, if any, at short time delay (within 1 ps) in heat-induced structural changes before phonons are highly excited, as discussed in this work.