Asymmetric tunneling conductance and the non-Fermi liquid behavior of strongly correlated Fermi systems
V. R. Shaginyan+*, A. Z. Msezane*, G. S. Japaridze*, V. A. Stephanovich×, Y. S. Leevik°
*Petersburg Nuclear Physics Institute of National Research Center "Kurchatov Institute", 188300 Gatchina, Russia
*Clark Atlanta University, GA 30314 Atlanta, USA
×Institute of Physics, Opole University, 45-052 Opole, Poland
°National Research University Higher School of Economics, 194100 St. Petersburg, Russia
Abstract
Tunneling differential conductivity (or resistivity) is a
sensitive tool to experimentally test the non-Fermi liquid
behavior of strongly correlated Fermi systems. In the case of
common metals the Landau-Fermi liquid theory demonstrates
that the differential conductivity is a symmetric function of
bias voltage V. This is because the particle-hole symmetry is
conserved in the Landau-Fermi liquid state. When a strongly correlated Fermi system
turns out to be near the topological fermion condensation
quantum phase transition, its Landau-Fermi liquid properties disappear so that
the particle-hole symmetry breaks making the differential
tunneling conductivity to be asymmetric function of V. This
asymmetry can be observed when a strongly correlated metal is in
its normal, superconducting or pseudogap states. We show that
the asymmetric part of the dynamic conductance does not depend
on temperature provided that the metal is in its superconducting
or pseudogap states. In normal state the asymmetric part
diminishes at rising temperatures. Under the application of
magnetic field the metal transits to the Landau-Fermi liquid state and the
differential tunneling conductivity becomes a symmetric function
of V. These findings are in good agreement with recent
experimental observations.