Date/Time Date(s) - 12/02/20083:00 pm - 4:00 pm
Title: Nonequilibrium Quantum Criticality in an Open Itinerant Electron
Speaker: Dr. So Takei
Institute: University of Toronto
Location: PB – 335
Description:
The study of critical phenomena in equilibrium many-body systems is by now a well-established subfield of condensed matter physics. The central issue in equilibrium critical phenomena is the emergence of universal behaviour among various systems with different microscopic properties when they are in the vicinity of a critical point. Whether or not this universality persists in systems driven far from equilibrium is an interesting but largely unexplored problem. In this talk, I will address this issue by considering a thin itinerant electron magnet driven into a nonequilibrium steady state by current flow across the system. The theory is formulated using the Keldysh functional integral formalism, and the renormalization group scheme is generalized to the nonequilibrium case to distinguish different universality classes of nonequilibrium perturbations. We show the relevance of departures from equilibrium at an equilibrium critical point and present the consequent decoupling of statics and dynamics by the nonequilibrium drive. By mapping our problem onto an effective classical theory we find that the leading effect of the nonequilibrium drive is to generate an effective temperature.