Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 48: Correlated Electrons: Quantum-Critical Phenomena - Theory
TT 48.5: Talk
Wednesday, March 13, 2013, 18:00–18:15, H19
Quantum Criticality in the two-channel pseudogap Anderson model — •Farzaneh Zamani1,2, Tathagata Chowdhury3, Pedro Ribeiro1,2, Kevin Ingersent3, and Stefan Kirchner3 — 1Max Planck Institute for the Physics of Complex System, Nöthnitzer Str. 38, D-01187 Dresden, Germany — 2Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, D-01187 Dresden, Germany — 3Department of Physics, University of Florida, Gainesville, Florida 32611-8440, USA
The two-channel Anderson impurity model with a density of states ρ(E)∝|E|r that vanishes at the Fermi energy (E = 0) is of current interest in connection with impurities in graphene and in unconventional superconductors. We study the dynamical properties of the two-channel Anderson model using the non-crossing approximation (NCA), and compare our results against the numerical renormalization-group (NRG) method. This model shows continuous quantum phase transitions between weak- and strong-coupling phases. The NCA is shown to reproduce the correct qualitative features of the pseudogap model, including the phase diagram, and to yield critical exponents in excellent agreement with the NRG and exact results. The forms of the dynamical magnetic susceptibility and impurity Green’s function at the fixed points are suggestive of frequency-over-temperature scaling, another aspect associated with interacting quantum critical points.