810 research outputs found
Electronic structure of the electron-doped cuprate superconductors
Within the framework of the kinetic energy driven d-wave superconductivity,
the electronic structure of the electron doped cuprate superconductors is
studied. It is shown that although there is an electron-hole asymmetry in the
phase diagram, the electronic structure of the electron-doped cuprates in the
superconducting-state is similar to that in the hole-doped case. With
increasing the electron doping, the spectral weight in the point
increases, while the position of the superconducting quasiparticle peak is
shifted towards the Fermi energy. In analogy to the hole-doped case, the
superconducting quasiparticles around the point disperse very weakly
with momentum.Comment: 8 pages, 3 figures, accepted for publication in Phys. Lett.
d-wave pairing symmetry in cuprate superconductors
Phase-sensitive tests of pairing symmetry have provided strong evidence for
predominantly d-wave pairing symmetry in both hole- and electron-doped high-Tc
cuprate superconductors. Temperature dependent measurements in YBCO indicate
that the d-wave pairing dominates, with little if any imaginary component, at
all temperatures from 0.5K through Tc. In this article we review some of this
evidence and discuss the implications of the universal d-wave pairing symmetry
in the cuprates.Comment: 4 pages, M2S 2000 conference proceeding
Enhancement of superconducting transition temperature by the additional second neighbor hopping t' in the t-J model
Within the kinetic energy driven superconducting mechanism, the effect of the
additional second neighbor hopping t' on the superconducting state of the t-J
model is discussed. It is shown that t' plays an important role in enhancing
the superconducting transition temperature of the t-J model. It is also shown
that the superconducting-state of cuprate superconductors is the conventional
Bardeen-Cooper-Schrieffer like, so that the basic Bardeen-Cooper-Schrieffer
formalism is still valid in quantitatively reproducing the doping dependence of
the superconducting gap parameter and superconducting transition temperature,
and electron spectral function at point, although the pairing
mechanism is driven by the kinetic energy by exchanging dressed spin
excitations.Comment: 8 pages, 4 figures, added discussions and references, accepted for
publication in Physics Letters
Renormalization Group Approach to Low Temperature Properties of a Non-Fermi Liquid Metal
We expand upon on an earlier renormalization group analysis of a non-Fermi
liquid fixed point that plausibly govers the two dimensional electron liquid in
a magnetic field near filling fraction . We give a more complete
description of our somewhat unorthodox renormalization group transformation by
relating both our field-theoretic approach to a direct mode elimination and our
anisotropic scaling to the general problem of incorporating curvature of the
Fermi surface. We derive physical consequences of the fixed point by showing
how they follow from renormalization group equations for finite-size scaling,
where the size may be set by the temperature or by the frequency of interest.
In order fully to exploit this approach, it is necessary to take into account
composite operators, including in some cases dangerous ``irrelevant''
operators. We devote special attention to gauge invariance, both as a formal
requirement and in its positive role providing Ward identities constraining the
renormalization of composite operators. We emphasize that new considerations
arise in describing properties of the physical electrons (as opposed to the
quasiparticles.) We propose an experiment which, if feasible, will allow the
most characteristic feature of our results, that isComment: 42 pages, 5 figures upon request, uses Phyzzx, IASSNS-HEP 94/6
Asymmetry of the electron spectrum in hole-doped and electron-doped cuprates
Within the t-t'-J model, the asymmetry of the electron spectrum and
quasiparticle dispersion in hole-doped and electron-doped cuprates is
discussed. It is shown that the quasiparticle dispersions of both hole-doped
and electron-doped cuprates exhibit the flat band around the (\pi,0) point
below the Fermi energy. The lowest energy states are located at the
(\pi/2,\pi/2) point for the hole doping, while they appear at the (\pi,0) point
in the electron-doped case due to the electron-hole asymmetry. Our results also
show that the unusual behavior of the electron spectrum and quasiparticle
dispersion is intriguingly related to the strong coupling between the electron
quasiparticles and collective magnetic excitations.Comment: 8 pages, 3 figures, typo corrected, added detailed calculations and
updated figure 3 and references, accepted for publication in Phys. Lett.
Mixing of superconducting state with s-wave states for different filling and temperature
We study the order parameter for mixed-symmetry states involving a major
state and various minor s-wave states (, , and
) for different filling and temperature for mixing angles 0 and
. We employ a two-dimensional tight-binding model incorporating
second-neighbor hopping for tetragonal and orthorhombic lattice. There is
mixing for the symmetric state both on tetragonal and orthorhombic lattice.
The state mixes with the state only on orthorhombic
lattice. The state never mixes with the state. The
temperature dependence of the order parameters is also studied.Comment: 10 pages, 9 figures, accepted in Physica
Proposed Measurement of an Effective Flux Quantum in the Fractional Quantum Hall Effect
We consider a channel of an incompressible fractional-quantum-Hall-effect
(FQHE) liquid containing an island of another FQHE liquid. It is predicted that
the resistance of this channel will be periodic in the flux through the island,
with the period equal to an odd integer multiple of the fundamental flux
quantum, . The multiplicity depends on the quasiparticle charges
of the two FQHE liquids.Comment: Late
On the Conductance Sum Rule for the Hierarchical Edge States of the Fractional Quantum Hall Effect
The conductance sum rule for the hierarchical edge channel currents of a
Fractional Quantum Hall Effect state is derived analytically within the
Haldane-Halperin hierarchy scheme. We provide also an intuitive interpretation
for the hierarchical drift velocities of the edge excitations.Comment: 11 pages, no figure, Revtex 3.0, IC/93/329, ASITP-93-5
Pairing symmetry and long range pair potential in a weak coupling theory of superconductivity
We study the superconducting phase with two component order parameter
scenario, such as, , where . We show, that in absence of orthorhombocity, the usual
does not mix with usual symmetry gap in an anisotropic band
structure. But the symmetry does mix with the usual d-wave for . The d-wave symmetry with higher harmonics present in it also mixes with
higher order extended wave symmetry. The required pair potential to obtain
higher anisotropic and extended s-wave symmetries, is derived by
considering longer ranged two-body attractive potential in the spirit of tight
binding lattice. We demonstrate that the dominant pairing symmetry changes
drastically from to like as the attractive pair potential is obtained
from longer ranged interaction. More specifically, a typical length scale of
interaction , which could be even/odd multiples of lattice spacing leads
to predominant wave symmetry. The role of long range interaction on
pairing symmetry has further been emphasized by studying the typical interplay
in the temperature dependencies of these higher order and wave pairing
symmetries.Comment: Revtex 8 pages, 7 figures embeded in the text, To appear in PR
Time reversal symmetry breaking superconductivity
We study time reversal symmetry breaking superconductivity with ( or )
symmetries. It is shown that the behavior of such superconductors could be {\em
qualitatively} different depending on the minor components () and its
phase at lower temperatures. It is argued that such {\em qualitatively
different} behaviors in thermal as well as in angular dependencies could be a
{\em source} of consequences in transport and Josephson physics.
Orthorhombicity is found to be a strong mechanism for mixed phase (in case of
). We show that due to electron correlation the order parameter is
more like a pure symmetry near optimum doping.Comment: 5 pages, 5 figures (attached), to be published in Physical Review
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