Electrons that conduct electricity but not heat
Prof. Junqiao Wu
Department of Materials Science and Engineering,
University of California, Berkeley
In conventional metals, itinerant electrons transport heat proportionally to the amount of electricity they transport, a fact known as the Wiedemann-Franz (W-F) law which is a hallmark of Fermi liquids. The law is robust in nearly all metals, with modest violations observed in exotic materials but all at low temperatures. We recently discovered [Science 355, 371 (2017)] a drastic violation of the W-F law above room temperature, where the electronic contribution to thermal conductivity amounts to only 10% of what is expected from the W-F law. The breakdown of the W-F law was observed in metallic tungsten vanadium dioxide in the vicinity of its metal-insulator transition. Different from previously established mechanisms, the unusually low electronic thermal conductivity is a signature of the absence of quasiparticles in transport of a strongly correlated electron fluid where heat and charge diffuse separately and independently. On the basis of these materials, we developed a reprogrammable meta-canvas on which arbitrary meta-photonic devices can be written, erased and re-written. Using the meta-canvas, we demonstrate dynamic manipulation of optical waves for light propagation, polarization and reconstruction.