Antimony thin films demonstrate programmable optical nonlinearity.

The use of metals of nanometer dimensions to enhance and manipulate light-matter interactions for emerging plasmonics-enabled nanophotonic and optoelectronic applications is an interesting yet not highly explored area of research beyond plasmonics. Even more importantly, the concept of an active metal that can undergo an optical nonvolatile transition has not been explored. Here, we demonstrate that antimony (Sb), a pure metal, is optically distinguishable between two programmable states as nanoscale thin films. We show that these states, corresponding to the crystalline and amorphous phases of the metal, are stable at room temperature. Crucially from an application standpoint, we demonstrate both its optoelectronic modulation capabilities and switching speed using single subpicosecond pulses. The simplicity of depositing a single metal portends its potential for use in any optoelectronic application where metallic conductors with an actively tunable state are important.