Band Structure Dynamics in Indium Wires

One-dimensional Indium wires grown on Si(111) substrates, which are metallic at high temperatures, become insulating below $\sim100$ K due to the formation of a Charge Density Wave (CDW). The physics of this transition is not conventional and involves a multiband Peierls instability with strong interband coupling. This CDW ground state is readily destroyed with femtosecond laser pulses resulting in a light-induced insulator-to-metal phase transition. The current understanding of this transition remains incomplete, requiring measurements of the transient electronic structure to complement previous investigations of the lattice dynamics. Time- and angle-resolved photo\-emission spectroscopy with extreme ultra-violet radiation is applied to this end. We find that the transition from the insulating to the metallic band structure occurs within $\sim660$ fs that is a fraction of the amplitude mode period. The long life time of the transient state ($>100$ ps) is attributed to trapping in a metastable state in accordance with previous work.