2,243 research outputs found
From d- to p-wave pairing in the t-t' Hubbard model at zero temperature
We develop a DCA(PQMC) algorithm which employs the projective quantum Monte
Carlo (PQMC) method for solving the equations of the dynamical cluster
approximation (DCA) at zero temperature, and apply it for studying pair
susceptibilities of the two-dimensional Hubbard-model with next-nearest
neighbor hopping. In particular, we identify which pairing symmetry is dominant
in the U-n parameter space (U: repulsive Coulomb interaction; n: electron
density). We find that p_{x+y}- (d_{x^2-y^2}-) wave is dominant among triplet
(singlet) pairings -at least for 0.3<n<0.8 and U<=4t. The crossover between
d_{x^2-y^2}-wave and p_{x+y}-wave occurs around n~0.4.Comment: 5 pages 5 figures; two additional panels in Fig. 2; as to appear in
Phys. Rev.
Semiclassical Analysis of the Supershell Effect in Reflection-Asymmetric Superdeformed Oscillator
An oscillatory pattern in the smoothed quantum spectrum, which is unique for
single-particle motions in a reflection-asymmetric superdeformed oscillator
potential, is investigated by means of the semiclassical theory of shell
structure. Clear correspondence between the oscillating components of the
smoothed level density and the classical periodic orbits is found. It is shown
that an interference effect between two families of the short periodic orbits,
called supershell effect, develops with increasing reflection-asymmetric
deformations. Possible origins of this enhancement phenomena as well as quantum
signatures of period-multipling bifurcations are discussed in connection with
stabilities of the classical periodic orbits.Comment: 27 pages, REVTeX, 12 postscript figures are available from the author
upon reques
Periodic Orbits and Deformed Shell Structure
Relationship between quantum shell structure and classical periodic orbits is
briefly reviewed on the basis of semi-classical trace formula. Using the
spheroidal cavity model, it is shown that three-dimensional periodic orbits,
which are born out of bifurcation of planar orbits at large prolate
deformations, generate the superdeformed shell structure.Comment: 8 pages including 8 figures, Talk at the Conference on Frontiers of
Nuclear Structure, July 29th - August 2nd, 2002, UC Berkele
Electronic Structure of Sodium Cobalt Oxide: Comparing Mono- and Bilayer-hydrate
To shed new light on the mechanism of superconductivity in sodium cobalt
oxide bilayer-hydrate (BLH), we perform a density functional calculation with
full structure optimization for BLH and its related nonsuperconducting phase,
monolayer hydrate (MLH). We find that these hydrates have similar band
structures, but a notable difference can be seen in the band around
the Fermi level. While its dispersion in the direction is negligibly small
for BLH, it is of the order of 0.1 eV for MLH. This result implies that the
three dimensional feature of the band may be the origin for the
absence of superconductivity in MLH.Comment: 5 pages, 7 figures, to be published in Phys. Rev.
Periodic-Orbit Bifurcation and Shell Structure in Reflection-Asymmetric Deformed Cavity
Shell structure of the single-particle spectrum for reflection-asymmetric
deformed cavity is investigated. Remarkable shell structure emerges for certain
combinations of quadrupole and octupole deformations. Semiclassical
periodic-orbit analysis indicates that bifurcation of equatorial orbits plays
an important role in the formation of this new shell structure.Comment: 5 pages, latex including 5 postscript figures, submitted to Physics
Letters
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