228 research outputs found
Vortex with Fractional Quantum Numbers in Chiral p-Wave Superconductor
We show that a vortex in a chiral p-wave superconductor, which has the p_{x}+
i p_{y}-wave pairing state and breaks U(1), parity and time reversal symmetry
simultaneously, has fractional charge -{n e}/{4} and fractional angular
momentum -n^{2}/{16} (n; vorticity). This suggests that the vortex could be
anyon and could obey fractional statistics. Electromagnetic property of the
vortex is also discussed and we find that an electric field is induced near the
vortex core.Comment: 10 pages, 3 figures, accepted for publication in Phys. Rev.
Thermal Conductivity near H_c2 for spin-triplet superconducting States with line nodes in Sr_2RuO_4
We calculate the thermal conductivity kappa in magnetic fields near H_c2 for
spin-triplet superconducting states with line nodes vertical and horizontal
relative to the RuO_2-planes. The method for calculating the Green's functions
takes into account the spatial variation of the order parameter and
superconducting flow for the Abrikosov vortex lattice. For in-plane magnetic
field we obtain variations of the in-plane kappa with two-fold symmetry as a
function of rotation angle where the minima and maxima occur for field
directions parallel and perpendicular to the heat flow. The amplitude of the
variation decreases with increasing impurity scattering and temperature. At
higher temperatures the minima and maxima of the variation are interchanged.
Since the results for vertical and horizontal line nodes are almost the same we
cannot say which of the two pairing models is more compatible with recent
measurements of kappa in Sr_2RuO_4. The observed four-fold modulation of kappa
in YBa_2Cu_3O_(7-\delta) is obtained for d-wave pairing by taking into account
the particular shape of the Fermi surface and the finite temperature effect.
The results for kappa for the f-wave pairing state with horizontal line nodes
disagree in some respects with the measurements on UPt_3.Comment: 8 pages, 6 figures. To be published in Phys. Rev.
Orbit spaces of free involutions on the product of two projective spaces
Let be a finitistic space having the mod 2 cohomology algebra of the
product of two projective spaces. We study free involutions on and
determine the possible mod 2 cohomology algebra of orbit space of any free
involution, using the Leray spectral sequence associated to the Borel fibration
. We also
give an application of our result to show that if has the mod 2 cohomology
algebra of the product of two real projective spaces (respectively complex
projective spaces), then there does not exist any -equivariant
map from for (respectively ), where
is equipped with the antipodal involution.Comment: 14 pages, to appear in Results in Mathematic
Spin Ordering and Quasiparticles in Spin Triplet Superconducting Liquids
Spin ordering and its effect on low energy quasiparticles in a p-wave
superconducting liquid are investigated. We show that there is a new 2D p-wave
superconducting liquid where the ground state is rotation invariant. In quantum
spin disordered liquids, the low energy quasiparticles are bound states of the
bare Bogolubov- De Gennes ({\em BdeG}) quasiparticles and zero energy
skyrmions, which are charge neutral bosons at the low energy limit. Further
more, spin collective excitations are fractionalized ones carrying a half spin
and obeying fermionic statistics. In thermally spin disordered limits, the
quasi-particles are bound states of bare {\em BdeG} quasi-particles. The
latter situation can be realized in some layered p-wave superconductors where
the spin-orbit coupling is weak.Comment: 5 pages, no figures; published versio
Theory of NMR as a local probe for the electronic structure in the mixed state of the high- cuprates
We argue that nuclear magnetic resonance experiments are a site-sensitive
probe for the electronic spectrum in the mixed state of the high-
cuprates. Within a spin-fermion model, we show that the Doppler-shifted
electronic spectrum arising from the circulating supercurrent changes the
low-frequency behavior of the imaginary part of the spin-susceptibility. For a
hexagonal vortex lattice, we predict that these changes lead to {\it (a)} a
unique dependence of the Cu spin lattice relaxation rate, , on
resonance frequency, and {\it (b)} a temperature dependence of which
varies with frequency. We propose a nuclear quadrupole experiment to study the
effects of a uniform supercurrent on the electronic structure and predict that
varies with the direction of the supercurrent.Comment: RevTex, 5 pages, 3 figures embedded in the tex
Atomistic Studies of Defect Nucleation during Nanoindentation of Au (001)
Atomistic studies are carried out to investigate the formation and evolution
of defects during nanoindentation of a gold crystal. The results in this
theoretical study complement the experimental investigations [J. D. Kiely and
J. E. Houston, Phys. Rev. B, v57, 12588 (1998)] extremely well. The defects are
produced by a three step mechanism involving nucleation, glide and reaction of
Shockley partials on the {111} slip planes noncoplanar with the indented
surface. We have observed that slip is in the directions along which the
resolved shear stress has reached the critical value of approximately 2 GPa.
The first yield occurs when the shear stresses reach this critical value on all
the {111} planes involved in the formation of the defect. The phenomenon of
strain hardening is observed due to the sessile stair-rods produced by the
zipping of the partials. The dislocation locks produced during the second yield
give rise to permanent deformation after retraction.Comment: 11 pages, 13 figures, submitted to Physical Review
Low temperature electronic properties of Sr_2RuO_4 II: Superconductivity
The body centered tetragonal structure of Sr_2RuO_4 gives rise to umklapp
scattering enhanced inter-plane pair correlations in the d_{yz} and d_{zx}
orbitals. Based on symmetry arguments, Hund's rule coupling, and a bosonized
description of the in-plane electron correlations the superconducting order
parameter is found to be a orbital-singlet spin-triplet with two spatial
components. The spatial anisotropy is 7%. The different components of the order
parameter give rise to two-dimensional gapless fluctuations. The phase
transition is of third order. The temperature dependence of the pair density,
specific heat, NQR, Knight shift, and susceptibility are in agreement with
experimental results.Comment: 20 pages REVTEX, 3 figure
Low temperature electronic properties of Sr_2RuO_4 III: Magnetic fields
Based on the microscopic model introduced previously the observed specific
heat and ac-susceptibility data in the superconducting phase in Sr_2RuO_4 with
applied magnetic fields are described consistently within a phenomenological
approach. Discussed in detail are the temperature dependence of the upper
critical fields H_{c2} and H_2, the dependence of the upper critical fields on
the field direction, the linear specific heat below the superconducting phase
transition as a function of field or temperature, the anisotropy of the two
spatial components of the order parameter, and the fluctuation field H_p.Comment: 8 pages REVTEX, 4 figure
Recent developments in unconventional superconductivity theory
The review of recent developments in the unconventional superconductivity
theory is given. In the fist part I consider the physical origin of the Kerr
rotation polarization of light reflected from the surface of superconducting
. Then the comparison of magneto-optical responses in
superconductors with orbital and spin spontaneous magnetization is presented.
The latter result is applied to the estimation of the magneto-optical
properties of neutral superfluids with spontaneous magnetization. The second
part is devoted to the natural optical activity or gyrotropy properties of
noncentrosymmetric metals in their normal and superconducting states. The
temperature behavior of the gyrotropy coefficient is compared with the
temperature behavior of paramagnetic susceptibility determining the noticeable
increase of the paramagnetic limiting field in noncentrosymmetric
superconductors. In the last chapter I describe the order parameter and the
symmetry of superconducting state in the itinerant ferromagnet with
orthorhombic symmetry. Finally the Josephson coupling between two adjacent
ferromagnet superconducting domains is discussed.Comment: 15 page
Field dependence of the vortex structure in chiral p-wave superconductors
To investigate the different vortex structure between two chiral pairing p_x
+(-) i p_y, we calculate the pair potential, the internal field, the local
density of states, and free energy in the vortex lattice state based on the
quasiclassical Eilenberger theory, and analyze the magnetic field dependence.
The induced opposite chiral component of the pair potential plays an important
role in the vortex structure. It also produces H^{1/2}-behavior of the
zero-energy density of states at higher field. These results are helpful when
we understand the vortex states in Sr2RuO4.Comment: 11 pages, 10 figures, to be published in Phys. Rev.
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