Figure 1

Figure 1: Schematic of how different fields affect the low-temperature equilibrium distribution of electrons in a Mott insulator (left). When driven by a dc field, the density of states Aω changes shape, but the occupancy Nω is similar to that of an equilibrium occupation at a positive temperature (top right). When driven by a high-frequency ac field, the interaction strength is renormalized, and the system can be at a negative temperature (bottom right).