989 research outputs found
Localizations in coupled electronic chains
We studied effects of random potentials and roles of electron-electron
interactions in the gapless phase of coupled Hubbard chains, using a
renormalization group technique. For non-interacting electrons, we obtained the
localization length proportional to the number of chains, as already shown in
the other approaches. For interacting electrons, the localization length is
longer for stronger interactions, that is, the interactions counteract the
random potentials. Accordingly, the localization length is not a simple linear
function of the number of chains. This interaction effect is strongest when
there is only a single chain. We also calculate the effects of interactions and
random potentials on charge stiffness.Comment: no figure, to appear in Phys. Rev.
Numerical study of a superconductor-insulator transition in a half-filled Hubbard chain with distant transfers
The ground state of a one-dimensional Hubbard model having the next-nearest
neighbor hopping (t') as well as the nearest-neighbor one (t) is numerically
investigated at half-filling. A quantum Monte Carlo result shows a slowly
decaying pairing correlation for a sizeable interaction strength ,
while the system is shown to become insulating for yet larger
from a direct evaluation of the charge gap with the density-matrix
renormalization group method. The results are consistent with Fabrizio's recent
weak-coupling theory which suggests a transition from a superconductor into an
insulator at a finite U.Comment: 4 pages, RevTeX, uses epsf.sty and multicol.st
Persistent current of two-chain Hubbard model with impurities
The interplay between impurities and interactions is studied in the gapless
phase of two-chain Hubbard model in order to see how the screening of impurity
potentials due to repulsive interactions in single-chain model will be changed
by increasing the number of channels. Renormalization group calculations show
that charge stiffness, and hence persistent current, of the two-chain model are
less enhanced by interactions than single chain case.Comment: 4 Pages, RevTeX, No figures, Submitted to PR
Effective induction heating around strongly magnetized stars
Planets that are embedded in the changing magnetic fields of their host stars
can experience significant induction heating in their interiors caused by the
planet's orbital motion. For induction heating to be substantial, the planetary
orbit has to be inclined with respect to the stellar rotation and dipole axes.
Using WX~UMa, for which the rotation and magnetic axes are aligned, as an
example, we show that for close-in planets on inclined orbits, induction
heating can be stronger than the tidal heating occurring inside Jupiter's
satellite Io; namely, it can generate a surface heat flux exceeding
2\,W\,m. An internal heating source of such magnitude can lead to
extreme volcanic activity on the planet's surface, possibly also to internal
local magma oceans, and to the formation of a plasma torus around the star
aligned with the planetary orbit. A strongly volcanically active planet would
eject into space mostly SO, which would then dissociate into oxygen and
sulphur atoms. Young planets would also eject CO. Oxygen would therefore be
the major component of the torus. If the O{\sc i} column density of the torus
exceeds 10\,cm, the torus could be revealed by detecting
absorption signatures at the position of the strong far-ultraviolet O{\sc i}
triplet at about 1304\,\AA. We estimate that this condition is satisfied if the
O{\sc i} atoms in the torus escape the system at a velocity smaller than
1--10\,km\,s. These estimates are valid also for a tidally heated
planet.Comment: 8 pages, 6 figures, accepted for publication in Ap
Phase diagram of the two-chain Hubbard model
We have calculated the charge gap and spin gap for the two-chain Hubbard
model as a function of the on-site Coulomb interaction and the interchain
hopping amplitude. We used the density matrix renormalization group method and
developed a method to calculate separately the gaps numerically for the
symmetric and antisymmetric modes with respect to the exchange of the chain
indices. We have found very different behaviors for the weak and strong
interaction cases. Our calculated phase diagram is compared to the one obtained
by Balents and Fisher using the weak coupling renormalization group technique.Comment: 4 pages, 6 figures, to appear in PR
Superconductivity in the three-leg Hubbard ladder: a Quantum Monte Carlo study
Quantum Monte Carlo method is used to look into the superconductivity in the
three-leg Hubbard ladder. The enhanced correlation for the pairing across the
central and edge chains, which has been predicted in the weak-coupling
renormalization as an effect of coexistence of gapful and gapless spin modes,
is here shown to persist for intermediate interaction strengths.Comment: 10 pages, RevTeX, 3 figures in PostScript file
Phase diagram of the half-filled Hubbard chain with next-nearest-neighbor hopping
We investigate the ground-state phase diagram of the half-filled
one-dimensional Hubbard model with next-nearest-neighbor hopping using the
Density-Matrix Renormalization Group technique as well as an unrestricted
Hartree-Fock approximation. We find commensurate and incommensurate disordered
magnetic insulating phases and a spin-gapped metallic phase in addition to the
one-dimensional Heisenberg phase. At large on-site Coulomb repulsion , we
make contact with the phase diagram of the frustrated Heisenberg chain, which
has spin-gapped phases for sufficiently large frustration. For weak ,
sufficiently large next-nearest-neighbor hopping leads to a band
structure with four Fermi points rather than two, producing a spin-gapped
metallic phase. As is increased in this regime, the system undergoes a
Mott-Hubbard transition to a frustrated antiferromagnetic insulator
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