Quantum Criticality in Heavy Fermion Metals

Condensed Matter Seminars

Speaker: Emilian Marius Nica, Department of Physics and Astronomy & Rice Center for Quantum Materials, Rice University
Date & Time: May 12, 2016, 2:00 - 3:00
Location: Hennings 318
Local Contact: Marcel Franz
Intended Audience: Graduate

Heavy fermion systems provide a prototype-setting for the study of strongly-correlated electrons. Experiments on heavy-fermion metals such as CeCu6-xAux, YbRh2Si2, and CeRhIn5 have generated a great deal of interest in the general context of magnetic quantum phase transitions and associated non-Fermi liquid behaviors. In contrast to transitions out of a spin-density-wave state, the suppression of magnetic order in these systems is simultaneous with a breakdown of the underlying heavy Fermi-liquid, manifested as an abrupt collapse of the entire Fermi surface. In order to account for this novel criticality and other possible unconventional transitions, a global phase diagram has emerged, which, in addition to the competition between the Kondo effect and the tendency towards magnetism, also incorporates the effects of the quantum fluctuations of the local moments. Concurrently, local criticality has emerged as a strong candidate for the description of unconventional quantum phase transitions in heavy-fermions. I will study such transitions within an Extended Dynamical Mean-Field theory of the Kondo lattice. In an Ising-anisotropic realization and in the presence of a transverse magnetic field, I will demonstrate local quantum criticality over a line of critical points in the global phase diagram. General implications of the results will be discussed.