11,275 research outputs found
Electronic States and Superconducting Transition Temperature based on the Tomonaga-Luttinger liquid in PrBaCuO
An NQR experiment revealed superconductivity of
PrBaCuO (Pr247) to be realized on CuO double chain
layers and suggests possibility of novel one-dimensional(1D) superconductivity.
To clarify the nature of the 1D superconductivity, we calculate the band
dispersions of Pr247 by using the generalized gradient approximation(GGA). It
indicates that Fermi surface of CuO double chains is well described to the
electronic structure of a quasi-1D system.
Assuming the zigzag Hubbard chain model to be an effective model of the
system, we derive tight binding parameters of the model from a fit to the
result of GGA. Based on the Tomonaga-Luttinger liquid theory, we estimate
transition temperature () of the quasi-1D zigzag Hubbard model from the
calculated value of the Luttinger liquid parameter . The result of
is consistent with that of experiments in Pr247 and it suggests that the
mechanism of the superconductivity is well understood within the concept of the
Tomonaga-Luttinger liquid.Comment: 4 pages, 5 figure
Modification of Angular Velocity by Inhomogeneous MRI Growth in Protoplanetary Disks
We have investigated evolution of magneto-rotational instability (MRI) in
protoplanetary disks that have radially non-uniform magnetic field such that
stable and unstable regions coexist initially, and found that a zone in which
the disk gas rotates with a super-Keplerian velocity emerges as a result of the
non-uniformly growing MRI turbulence. We have carried out two-dimensional
resistive MHD simulations with a shearing box model. We found that if the
spatially averaged magnetic Reynolds number, which is determined by widths of
the stable and unstable regions in the initial conditions and values of the
resistivity, is smaller than unity, the original Keplerian shear flow is
transformed to the quasi-steady flow such that more flattened (rigid-rotation
in extreme cases) velocity profile emerges locally and the outer part of the
profile tends to be super-Keplerian. Angular momentum and mass transfer due to
temporally generated MRI turbulence in the initially unstable region is
responsible for the transformation. In the local super-Keplerian region,
migrations due to aerodynamic gas drag and tidal interaction with disk gas are
reversed. The simulation setting corresponds to the regions near the outer and
inner edges of a global MRI dead zone in a disk. Therefore, the outer edge of
dead zone, as well as the inner edge, would be a favorable site to accumulate
dust particles to form planetesimals and retain planetary embryos against type
I migration.Comment: 28 pages, 11figures, 1 table, accepted by Ap
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