Magyar Tudományos Akadémia
(Center for Materials Theory, Rutgers University)
Quantum Criticality: towards a new universality
Empirically, Quantum criticality appears to be a vital mechanism for driving novel material behavior in condensed matter. Recent experiments suggest that to understand this new phenomenon, we will have to significantly revise our understanding about phase transitions. I will discuss very new experiments which indicate that the characteristic energy scale of Fermi liquid excitations collapses over the entire Fermi surface of a heavy electron system at a quantum critical point, even in a manifestly cubic, three dimensional material. New data also suggest that the Hall constant "jumps" at the same QCP, suggesting a sudden collapse of the heavy electron Fermi surface when magnetism develops. I will explain why these results implicate a truly fundamental break-down in our basic understanding of how magnetism develops in a heavy electron fluid and discuss our recent efforts to develop a new class of mean-field theory that can span the magnetic quantum critical point in heavy electron materials.