Ultrafast electronic disorder in heat-induced structural deformations and phase transitions in metals

Heat-induced structural deformations and phase transitions of gold and silver are studied using 1.55-eV, 120-fs ultrashort laser pulses. The dynamics of the heating process is monitored by measuring the time evolution of the dielectric constants following optical excitation. Intensity-dependent dielectric constants in silver and gold show similarities with the photon-energy-dependent dielectric constants, which is shown to indirectly map out the degree of heat-induced electronic disorder in these noble metals. This observation strongly suggests that the heat-induced structural deformations and phase transitions in metals are tied to the electronic disorder and band-structure collapse.