4,486 research outputs found
Nuclear Spin Relaxation Rate of Disordered -wave Superconductors
Based on an effective Hamiltonian with the binary alloy disorder model
defined in the triangular lattice, the impurity scattering effects on the
density of states and especially on the spin-lattice relaxation rate of
-wave superconductors are studied by solving numerically the
Bogoliubov-de Gennes equations. In the clean limit, the coherence peak of
is observed as expected. More intriguingly, for strong scattering
potential, the temperature dependence of exhibits the two different
power law behaviors near and at low temperatures, respectively,
which is in good agreement with the nuclear quadrupolar resonance measurement.Comment: 4 pages, 3 figure
Vortex State in Na_xCoO_2.yH_2O: p_x\pm ip_y-wave versus d_{x^2-y^2}\pm id_{xy}-wave Pairing
Based on an effective Hamiltonian specified in the triangular lattice with
possible - or -wave pairing, which has
close relevance to the newly discovered NaCoOHO, the
electronic structure of the vortex state is studied by solving the
Bogoliubov-de Gennes equations. It is found that -wave is favored
for the electron doping as the hopping integral . The lowest-lying vortex
bound states are found to have respectively zero and positive energies for
- and -wave superconductors, whose vortex
structures exhibit the intriguing six-fold symmetry. In the presence of strong
on-site repulsion, the antiferromagnetic and ferromagnetic orders are induced
around the vortex cores for the former and the latter, respectively, both of
which cause the splitting of the LDOS peaks due to the lifting of spin
degeneracy. STM and NMR measurements are able to probe the new features of
vortex states uncovered in this work.Comment: 4 pages, 4 figures, The slightly shorter version was submitted to PR
Pseudogap and Fermi-arc Evolution in the Phase-fluctuation Scenario
Pseudogap phenomena and the formation of Fermi arcs in underdoped cuprates
are numerically studied in the presence of phase fluctuations that are
simulated by an XY model. Most importantly the spectral function for each Monte
Carlo sample is calculated directly and efficiently by the Chebyshev
polynomials without having to diagonalize the fermion Hamiltonian, which
enables us to handle a system large enough to achieve sufficient
momentum/energy resolution. We find that the momentum dependence of the energy
gap is identical to that of a pure d-wave superconductor well below the
KT-transition temperature (), while displays an upturn deviation from
with increasing temperature. An abrupt onset of the Fermi
arcs is observed above and the arc length exhibits a similar
temperature dependence to the thermally activated vortex excitations.Comment: 5 pages, 4 figure
Left-Right Asymmetry of Weak Interaction Mass of Polarized Fermions in Flight
The left-right polarization-dependent asymmetry of the weak interaction mass
is investigated. Based on the Standard Model, the calculation shows that the
weak interaction mass of left-handed polarized fermions is always greater than
that of right-handed polarized fermions in flight with the same velocity in any
inertial frame. The asymmetry of the weak interaction mass might be very
important to the investigation of neutrino mass and would have an important
significance for understanding the parity nonconservation in weak interactions.Comment: 8 pages, 2 figures, corrected calculatio
Transverse spin effects of sea quarks in unpolarized nucleons
We calculate the non-zero Boer-Mulders functions of sea quarks inside the
proton in a meson-baryon fluctuation model. The results show that the
transverse spin effects of sea quarks in an unpolarized nucleon are sizable.
Using the obtained antiquark Boer-Mulders functions, we estimate the asymmetries in the unpolarized and Drell-Yan processes at FNAL
E866/NuSea experiments. The prediction for the asymmetries in the
unpolarized Drell-Yan process at the BNL Relativistic Heavy Ion Collider
(RHIC) is also given.Comment: 7 pages, 5 figures, to appear in Physical Review
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