857 research outputs found
Andreev Bound states in One Dimensional Topological Superconductor
We study the charge character of the Andreev bound states (ABSs) in
one-dimensional topological superconductors with spatial inversion symmetry
(SIS) breaking. Despite the absence of the SIS, we show a hidden symmetry for
the Bogoliubov de Gennes equations around Fermi points in addition to the
particle-hole symmetry. This hidden symmetry protects that the charge of the
ABSs is solely dependent on the corresponding Fermi velocities. On the other
hand, if the SIS is present, the ABSs are charge neutral, similar to Majorana
fermions. We demonstrate that the charge of the ABSs can be experimentally
measured in the tunneling transport spectroscopy from the resonant differential
tunneling conductance.Comment: 4 pages plus appendix; 4 figure
Linear Response Theory and the Universal Nature of the Magnetic Excitation Spectrum of the Cuprates
Linear response theory, commonly known as the random phase approximation
(RPA), predicts a rich magnetic excitation spectrum for d-wave superconductors.
Many of the features predicted by such calculations appear to be reflected in
inelastic neutron scattering data of the cuprates. In this article, I will
present results from RPA calculations whose input is based on angle resolved
photoemission data, and discuss possible relevance to inelastic neutron
scattering data of LSCO, YBCO, and Bi2212 in their superconducting and
non-superconducting phases. In particular, the question of the universality of
the magnetic excitation spectrum will be addressed.Comment: 9 pages, 13 figure
Coherent Inverse Photoemission Spectrum for Gutzwiller Projected Superconductors
Rigorous relations for Gutzwiller projected BCS states are derived. The
obtained results do not depend on the details of model systems, but solely on
the wave functions. Based on the derived relations, physical consequences are
discussed for strongly correlated superconducting states such as high- cuprate superconductors.Comment: 4 pages, 3 figures, to be published in Phys. Rev.
Anomalous Zeeman response in coexisting phase of superconductivity and spin-density wave as a probe of extended -wave pairing structure in ferro-pnictide
In several members of the ferro-pnictides, spin density wave (SDW) order
coexists with superconductivity over a range of dopings. In this letter we
study the anomalous magnetic Zeeman response of this coexistence state and show
that it can be used to confirm the extended s-wave gap structure as well as
structure of superconducting (SC) gap in coexisting phase. On increasing the
field, a strongly anisotropic reduction of SC gap is found. The anisotropy is
directly connected to the gap structure of superconducting phase. The signature
of this effect in quasiparticle interference measured by STM, as well as heat
transport in magnetic field is discussed. For the compounds with the nodal SC
gap we show that the nodes are removed upon formation of SDW. Interestingly the
size of the generated gap in the originally nodal areas is anisotropic in the
position of the nodes over the Fermi surface in direct connection with the form
of SC pairing.Comment: 5 pages, 2 figure
Vertex correction and Ward identity in the U(1) gauge theory with Fermi surface
We show that introduction of vertex corrections in the fully self-consistent
ladder approximation does not modify dynamics of spinons and gauge fluctuations
in the U(1) gauge theory with Fermi surface
Weak phase stiffness and mass divergence of superfluid in underdoped cuprates
Despite more than two decades of intensive investigations, the true nature of
high temperature (high-) superconductivity observed in the cuprates
remains elusive to the researchers. In particular, in the so-called
`underdoped' region, the overall behavior of superconductivity deviates
from the standard theoretical description pioneered by Bardeen,
Cooper and Schrieffer (BCS). Recently, the importance of phase fluctuation of
the superconducting order parameter has gained significant support from various
experiments. However, the microscopic mechanism responsible for the
surprisingly soft phase remains one of the most important unsolved puzzles.
Here, opposite to the standard BCS starting point, we propose a simple,
solvable low-energy model in the strong coupling limit, which maps the
superconductivity literally into a well-understood physics of superfluid in a
special dilute bosonic system of local pairs of doped holes. In the
prototypical material (LaSr)CuO, without use of
any free parameter, a -wave superconductivity is obtained for doping above
, below which unexpected incoherent -wave pairs dominate.
Throughout the whole underdoped region, very soft phases are found to originate
from enormous mass enhancement of the pairs. Furthermore, a striking mass
divergence is predicted that dictates the occurrence of the observed quantum
critical point. Our model produces properties of the superfluid in good
agreement with the experiments, and provides new insights into several current
puzzles. Owing to its simplicity, this model offers a paradigm of great value
in answering the long-standing challenges in underdoped cuprates
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