  Vanadium dioxide (VO2) is a phase change material that can reversibly change
between high and low resistivity states through electronic and structural phase
transitions. Thus far, VO2 memory devices have essentially been volatile at
room temperature, and nonvolatile memory has required non-ambient surroundings
(e.g., elevated temperatures, electrolytes) and long write times. Here, we
report the first observation of optically addressable nonvolatile memory in VO2
at room temperature with a readout by voltage oscillations. The read and write
times had to be kept shorter than about 150 {\mu}s. The writing of the memory
and onset of the voltage oscillations had a minimum optical power threshold.
This discovery demonstrates the potential of VO2 for new computing devices and
architectures, such as artificial neurons and oscillatory neural networks.
