4 research outputs found
Doping dependence of the vortex-core energy in bilayer films of cuprates
The energy needed to create a vortex core is the basic ingredient to address
the physics of thermal vortex fluctuations in underdoped cuprates. Here we
theoretically investigate its role on the occurrence of the
Beresinskii-Kosterlitz-Thouless transition in a bilayer film with
inhomogeneity. From the comparison with recent measurements of the penetration
depth in two-unit cell thin films of
YCaBaCuO_{7-\d} (YBCO) by Hetel et al. [Nat. Phys.
3, 700 (2007)] we can extract the value of the vortex-core energy , and
show that scales linearly with at low doping.Comment: 4pages, 3 figures. References added, final versio
Broadening of the Beresinkii-Kosterlitz-Thouless superconducting transition by inhomogeneity and finite-size effects
We discuss the crucial role played by finite-size effects and inhomogeneity
on the Beresinkii-Kosterlitz-Thouless (BKT) transition in two-dimensional
superconductors. In particular, we focus on the temperature dependence of the
resistivity, that is dominated by superconducting fluctuations above the BKT
transition temperature and by inhomogeneity below it. By means of a
renormalization-group approach we establish a direct correspondence between the
parameter values used to describe the BKT fluctuation regime and the distance
between and the mean-field Ginzburg-Landau transition temperature.
Below a resistive tail arises due to finite-size effect and
inhomogeneity, that reflects also on the temperature dependence of the
superfluid density. We apply our results to recent experimental data in
superconducting LaAlO/SrTiO heterostructures, and we extract several
informations on the microscopic properties of the system from our BKT fitting
parameters. Finally, we compare our approach to recent data analysis presented
in the literature, where the physical meaning of the parameter values in the
BKT formulas has been often overlooked.Comment: 11 pages, 9 figures, final versio
Sine-Gordon description of Beresinskii-Kosterlitz-Thouless physics at finite magnetic field
The Beresinskii-Kosterlitz-Thouless (BKT) physics of vortices in
two-dimensional superconductors at finite magnetic field is investigated by
means of a field-theoretical approach based on the sine-Gordon model. This
description leads to a straightforward definition of the field-induced
magnetization and shows that the persistence of non-linear effects at low
fields above the transition is a typical signature of the fast divergence of
the correlation length within the BKT theory.Comment: 4 pages, 2 figures, to appear on Physical Review Letter
Applicability of layered sine-Gordon models to layered superconductors: II. The case of magnetic coupling
In this paper, we propose a quantum field theoretical renormalization group
approach to the vortex dynamics of magnetically coupled layered
superconductors, to supplement our earlier investigations on the
Josephson-coupled case. We construct a two-dimensional multi-layer sine-Gordon
type model which we map onto a gas of topological excitations. With a special
choice of the mass matrix for our field theoretical model, vortex dominated
properties of magnetically coupled layered superconductors can be described.
The well known interaction potentials of fractional flux vortices are
consistently obtained from our field-theoretical analysis, and the physical
parameters (vortex fugacity and temperature parameter) are also identified. We
analyse the phase structure of the multi-layer sine--Gordon model by a
differential renormalization group method for the magnetically coupled case
from first principles. The dependence of the transition temperature on the
number of layers is found to be in agreement with known results based on other
methods.Comment: 7 pages, 1 figure, published in J. Phys.: Condens. Matte