Gang Cao: Quest for Novel States of Matter

"Quest for Novel States of Matter"

Abstract: Our research has focused on the discovery, synthesis, and study of novel quantum materials. In this talk, I report two of our most recent discoveries: A chiral-orbital-currents state that underpins a novel colossal magnetoresistance, a first-order bistable state and a strongly current-sensitive Hall effect in ferrimagnetic Mn3Si2Te6, and A heavy Fermi surface of chargeneutral spinons that supports both a heavy-fermion strange metal and adjacent quantum-spin-liquid phases in the 4d-electron trimer lattice Ba4Nb1-xRu3+xO12 (without f electrons). The extraordinarily large entropy, linear heat capacity and thermal conductivity of both phases extend into milli-Kelvin temperatures, which is best explained by charge and spin dissociation. The insulating spin liquid is a much better thermal conductor than the heavy-fermion strange metal that is separately observed to strongly violate the Wiedemann- Franz law. The novel phenomenology offers a new paradigm of correlated quantum matter.