Contrasting Different Scenarios for the Quantum Critical Point
V. A. Khodel+*, J. W. Clark*, M. V. Zverev+
+Russian Research Centre Kurchatov Institute, 123182 Moscow, Russia
*McDonnell Center for the Space Science and Department of Physics,
Washington University, MO 63130, USA
PACS: 71.10.Hf, 71.27.+a
Abstract
Competing scenarios for quantum critical points (QCPs) of strongly
interacting Fermi systems signaled by a divergent density of
states at zero temperature are contrasted. The conventional
scenario, which enlists critical fluctuations of a collective
mode and attributes the divergence to a coincident vanishing of
the quasiparticle strength z, is shown to be incompatible
with identities arising from conservation laws prevailing in the
fermionic medium. An alternative scenario, in which the topology
of the Fermi surface is altered at the QCP, is found to explain
the non-Fermi-liquid thermodynamic behavior observed experimentally in
Yb-based compounds close to the QCP. It is suggested that combination
of the topological scenario with the theory of quantum phase
transitions will provide a proper foundation for analysis of
the extended QCP region.