How to Dress a Metal
Research describing how an optical field can modify the electronic properties of a solid was recently published in Nature Communications titled "Coherent multidimensional photoelectron spectroscopy of ultrafast quasiparticle dressing by light", coauthored by Dr. Marcel Reutzel, Hrvoje Petek, and Petek's students Andi Li and Zehua Wang.
Applying intense ultrafast light pulses, which provide a time-periodic electronic potential acting together with the lattice ions, defines the forces experienced by electrons in solids, such as metals and semiconductors, Petek and his coworkers demonstrated that an optical field can transiently, on the 10-14 second time scale, modify (dress) the electronic bands in a metal, potentially changing them from an electron to a hole condition.
This is important because electron and hole quasiparticles move in the opposite direction in response to an applied electrical field. They demonstrate that light can be used to modify electronic band structures of solids as fast as the attosecond (less than 10^-15 second) time scale of oscillation of the optical field of visible light. This could be used for applications ranging from quantum computing to switching of electrical currents a thousand times faster than in any electronic devices in use today.