15 research outputs found
Superconducting zero temperature phase transition in two dimensions and in the magnetic field
We derive the Ginzburg-Landau-Wilson theory for the superconducting phase
transition in two dimensions and in the magnetic field. Without disorder the
theory describes a fluctuation induced first-order quantum phase transition
into the Abrikosov lattice. We propose a phenomenological criterion for
determining the transition field and discuss the qualitative effects of
disorder. Comparison with recent experiments on MoGe films is discussed.Comment: 7 pages, 2 figure
Transport Properties near the z=2 Insulator-Superconductor Transition
We consider here the fluctuation conductivity near the point of the
insulator-superconductor transition in a system of regular Josephson junction
arrays in the presence of particle-hole asymmetry or equivalently homogeneous
charge frustration. The transition is characterised by the dynamic critical
exponent , opening the possibility of the perturbative
renormalization-group (RG) treatment. The quartic interaction in the
Ginzburg-Landau action and the coupling to the Ohmic heat bath, giving the
finite quasiparticle life-time, lead to the non-monotonic behavior of the dc
conductivity as a function of temperature in the leading logarithmic
approximation.Comment: Revised version for publication. To appear in PR
Scaling critical behavior of superconductors at zero magnetic field
We consider the scaling behavior in the critical domain of superconductors at
zero external magnetic field. The first part of the paper is concerned with the
Ginzburg-Landau model in the zero magnetic field Meissner phase. We discuss the
scaling behavior of the superfluid density and we give an alternative proof of
Josephson's relation for a charged superfluid. This proof is obtained as a
consequence of an exact renormalization group equation for the photon mass. We
obtain Josephson's relation directly in the form , that
is, we do not need to assume that the hyperscaling relation holds. Next, we
give an interpretation of a recent experiment performed in thin films of
. We argue that the measured mean field like
behavior of the penetration depth exponent is possibly associated with a
non-trivial critical behavior and we predict the exponents and
for the correlation lenght and specific heat, respectively. In the
second part of the paper we discuss the scaling behavior in the continuum dual
Ginzburg-Landau model. After reviewing lattice duality in the Ginzburg-Landau
model, we discuss the continuum dual version by considering a family of
scalings characterized by a parameter introduced such that
, where is the bare mass of the magnetic
induction field. We discuss the difficulties in identifying the renormalized
magnetic induction mass with the photon mass. We show that the only way to have
a critical regime with is having , that
is, with having the scaling behavior of the renormalized photon mass.Comment: RevTex, 15 pages, no figures; the subsection III-C has been removed
due to a mistak
Influence of thermal fluctuations on quantum phase transitions in one-dimensional disordered systems: Charge density waves and Luttinger liquids
The low temperature phase diagram of 1D weakly disordered quantum systems
like charge or spin density waves and Luttinger liquids is studied by a
\emph{full finite temperature} renormalization group (RG) calculation. For
vanishing quantum fluctuations this approach is amended by an \emph{exact}
solution in the case of strong disorder and by a mapping onto the \emph{Burgers
equation with noise} in the case of weak disorder, respectively. At \emph{zero}
temperature we reproduce the quantum phase transition between a pinned
(localized) and an unpinned (delocalized) phase for weak and strong quantum
fluctuations, respectively, as found previously by Fukuyama or Giamarchi and
Schulz.
At \emph{finite} temperatures the localization transition is suppressed: the
random potential is wiped out by thermal fluctuations on length scales larger
than the thermal de Broglie wave length of the phason excitations. The
existence of a zero temperature transition is reflected in a rich cross-over
phase diagram of the correlation functions. In particular we find four
different scaling regions: a \emph{classical disordered}, a \emph{quantum
disordered}, a \emph{quantum critical} and a \emph{thermal} region. The results
can be transferred directly to the discussion of the influence of disorder in
superfluids. Finally we extend the RG calculation to the treatment of a
commensurate lattice potential. Applications to related systems are discussed
as well.Comment: 19 pages, 7 figure