3,281 research outputs found
Semi-Meissner state and neither type-I nor type-II superconductivity in multicomponent systems
Traditionally, superconductors are categorized as type-I or type-II. Type-I
superconductors support only Meissner and normal states, while type-II
superconductors form magnetic vortices in sufficiently strong applied magnetic
fields. Recently there has been much interest in superconducting systems with
several species of condensates, in fields ranging from Condensed Matter to High
Energy Physics. Here we show that the type-I/type-II classification is
insufficient for such multicomponent superconductors. We obtain solutions
representing thermodynamically stable vortices with properties falling outside
the usual type-I/type-II dichotomy, in that they have the following features:
(i) Pippard electrodynamics, (ii) interaction potential with long-range
attractive and short-range repulsive parts, (iii) for an n-quantum vortex, a
non-monotonic ratio E(n)/n where E(n) is the energy per unit length, (iv)
energetic preference for non-axisymmetric vortex states, "vortex molecules".
Consequently, these superconductors exhibit an emerging first order transition
into a "semi-Meissner" state, an inhomogeneous state comprising a mixture of
domains of two-component Meissner state and vortex clusters.Comment: in print in Phys. Rev. B Rapid Communications. v2: presentation is
made more accessible for a general reader. Latest updates and links to
related papers are available at the home page of one of the authors:
http://people.ccmr.cornell.edu/~egor
Thermodynamics of Crossover from Weak- to Strong-Coupling Superconductivity
In this paper we study an evolution of low-temperature thermodynamical
quantities for an electron gas with a -function attraction as the
system crosses over from weak-coupling (BCS-type) to strong-coupling
(Bose-type) superconductivity in three and two dimensions.Comment: Replaced with journal version. Insignificant presentation changes.
Links to related papers are also available at the author home page
http://www.teorfys.uu.se/PEOPLE/egor
Muon-spin rotation measurements of the vortex state in SrRuO: type-1.5 superconductivity, vortex clustering and a crossover from a triangular to a square vortex lattice
Muon-spin rotation has been used to probe vortex state in SrRuO. At
moderate fields and temperatures a lattice of triangular symmetry is observed,
crossing over to a lattice of square symmetry with increasing field and
temperature. At lower fields it is found that there are large regions of the
sample that are completely free from vortices which grow in volume as the
temperature falls. Importantly this is accompanied by {\it increasing} vortex
density and increasing disorder within the vortex-cluster containing regions.
Both effects are expected to result from the strongly temperature-dependent
long-range vortex attractive forces arising from the multi-band chiral-order
superconductivity.Comment: 13 pages, 4 figure
Fractional-flux vortices and spin superfluidity in triplet superconductors
We discuss a novel type of fractional flux vortices along with integer flux
vortices in Kosterlitz-Thouless transitions in a triplet superconductor. We
show that under certain conditions a spin-triplet superconductor should exhibit
a novel state of {\it spin superfluidity} without superconductivity.Comment: Physical Review Lettes, in print. v2: references added, v3:
discussion of several points extended according to referee request. Latest
updates and links to related papers are available at my homepage
http://people.ccmr.cornell.edu/~egor
Baryonic Bound State of Vortices in Multicomponent Superconductors
We construct a bound state of three 1/3-quantized Josephson coupled vortices
in three-component superconductors with intrinsic Josephson couplings, which
may be relevant with regard to iron-based superconductors. We find a Y-shaped
junction of three domain walls connecting the three vortices, resembling the
baryonic bound state of three quarks in QCD. The appearance of the Y-junction
(but not a Delta-junction) implies that in both cases of superconductors and
QCD, the bound state is described by a genuine three-body interaction (but not
by the sum of two-body interactions). We also discuss a
confinement/deconfinement phase transition.Comment: 11 pages, 3 figures, one section on confinement/deconfinement
transition added, published versio
Semi-Meissner state and non-pairwise intervortex interactions in type-1.5 superconductors
We demonstrate existence of non-pairwise interaction forces between vortices
in multicomponent and layered superconducting systems. That is, in contrast to
most common models, the interactions in a group of such vortices is not a
universal superposition of Coulomb or Yukawa forces. Next we consider the
properties of vortex clusters in Semi-Meissner state of type-1.5 two-component
superconductors. We show that under certain condition non-pairwise forces can
contribute to formation of very complex vortex states in type-1.5 regimes.Comment: v2: replaced with version to appear in Phys.Rev. B. Substantially
exteded, title changed. Animation of the vortex clusters formation in
type-1.5 superconductors is available at
http://people.umass.edu/garaud/NonPairwise.htm
Vortex coalescence and type-1.5 superconductivity in Sr2RuO4
Recently vortex coalescence was reported in superconducting Sr2RuO4 by
several experimental groups for fields applied along the c-axis. We argue that
Sr2RuO4 is a type-1.5 superconductor with long-range attractive, short-range
repulsive intervortex interaction. The type-1.5 behavior stems from an
interplay of the two orbital degrees of freedom describing this chiral
superconductor together with the multiband nature of the superconductivity.
These multiple degrees of freedom give rise to multiple coherence lengths, some
of which are larger and some smaller than the magnetic field penetration
length, resulting in nonmonotonic intervortex forces.Comment: To appear in Physical Review B Rapid Communications. Minor additions
following referees suggestions; References added. 5 pages, 2 figure
BCS-Bose Crossover in Color Superconductivity
It is shown that the onset of the color superconducting phase occurs in the
BCS-BE crossover region.Comment: 5 pages, LaTeX, references adde
Frontiers, challenges, and solutions in modeling of swift heavy ion effects in materials
Since a few breakthroughs in the fundamental understanding of the effects of
swift heavy ions (SHI) decelerating in the electronic stopping regime in the
matter have been achieved in the last decade, it motivated us to review the
state-of-the-art approaches in the modeling of SHI effects. The SHI track
kinetics occurs via several well-separated stages: from attoseconds in
ion-impact ionization depositing energy in a target, to femtoseconds of
electron transport and hole cascades, to picoseconds of lattice excitation and
response, to nanoseconds of atomic relaxation, and even longer macroscopic
reaction. Each stage requires its own approaches for quantitative description.
We discuss that understanding the links between the stages makes it possible to
describe the entire track kinetics within a multiscale model without fitting
procedures. The review focuses on the underlying physical mechanisms of each
process, the dominant effects they produce, and the limitations of the existing
approaches as well as various numerical techniques implementing these models.
It provides an overview of ab-initio-based modeling of the evolution of the
electronic properties; Monte Carlo simulations of nonequilibrium electronic
transport; molecular dynamics modeling of atomic reaction on the surface and in
the bulk; kinetic Mote Carlo of atomic defect kinetics; finite-difference
methods of tracks interaction with chemical solvents describing etching
kinetics. We outline the modern methods that couple these approaches into
multiscale multidisciplinary models and point to their bottlenecks, strengths,
and weaknesses. The analysis is accompanied by examples of important results
improving the understanding of track formation in various materials.
Summarizing the most recent advances in the field of the track formation
process, the review delivers a comprehensive picture and detailed understanding
of the phenomena.Comment: to be submitte
- …