Junqiao Wu1 Lei Jin1 Kechao Tang1 Jiachen Li1 Kaichen Dong1 Jie Yao1

1, University of California, Berkeley, Berkeley, California, United States

In conventional metals, itinerant electrons carry both charge and heat. As a consequence, electrical conductivity and the electronic contribution to thermal conductivity are typically proportional to each other, known as the Wiedemann-Franz law that is robust in all conventional metals known as Fermi liquids. We found a large violation of this law near the insulator-metal phase transition in metallic vanadium dioxide (VO2). In the metallic phase, the electronic contribution to thermal conductivity amounts to only 10% of what would be expected from the Wiedemann-Franz law. The results are explained in terms of independent propagation of charge and heat in a strongly correlated electron system, where the electrons move in unison in a new, non-quasiparticle mode. In contrast, chemical doping and artificial introduction of point defects in VO2 apparently recover its behavior toward normal metals, opening opportunities to discovery of new physics as well as new applications of the metal-insulator transition. Utilizing the phase transition in VO2 films, we develop a lithography-free, rewritable “meta-canvas” on which nearly arbitrary photonic devices can be rapidly and repeatedly written and erased. Using the meta-canvas, we demonstrate dynamic manipulation of optical waves for light propagation, polarization and reconstruction.