44 research outputs found
Non-universal weak antilocalization effect in cubic topological Kondo insulators
We study the quantum correction to conductivity on the surface of cubic
topological Kondo insulators with multiple Dirac bands. We consider the model
of time-reversal invariant disorder which induces the scattering of the
electrons within the Dirac bands as well as between the bands. When only
intraband scattering is present we find three long-range diffusion modes which
lead to weak antilocalization correction to conductivity, which remains
independent of the microscopic details such as Fermi velocities and relaxation
times. Interband scattering gaps out two diffusion modes leaving only one
long-range mode. We find that depending on the value of the phase coherence
time, either three or only one long-range diffusion modes contribute to weak
localization correction rendering the quantum correction to conductivity
non-universal. We provide an interpretation for the results of the recent
transport experiments on samarium hexaboride where weak antilocalization has
been observed.Comment: 15 pages, 7 figure
Transport anomalies in multiband superconductors near quantum critical point
We study the effects of quantum fluctuations on the transport properties of
multiband superconductors near a pair-breaking quantum critical point. For this
purpose, we consider a minimal model of the quantum phase transition in a
system with two nested two-dimensional Fermi surfaces. Under the assumption
that doping the system adds nonmagnetic impurities but does not change the
densities of carriers, we include disorder potentials that render both intra-
and interband collisions. Interband scattering leads to full suppression of the
unconventional superconducting order similar to the effect of
paramagnetic impurities in isotropic single-band superconductors. We use the
diagrammatic technique of quantum field theory to compute the corrections to
electrical conductivity in a normal state due to superconducting fluctuations
in the entire low-temperature quantum regime. We show that the sign of the
conductivity correction depends on how the quantum critical point is approached
in the phase diagram. We contrast our findings to existing approaches to this
problem based on the renormalization group, time-dependent Ginzburg-Landau
phenomenology, and effective bosonic action field theories.Comment: 43 pages, 12 figures, 4 table