717 research outputs found
Numerical Study of Two-fluid Flowing Equilibria of Helicity-driven Spherical Torus Plasmas
Two-fluid flowing equilibrium configurations of a helicity-driven spherical
torus (HD-ST) are numerically determined by using the combination of the finite
difference and the boundary element methods. It is found from the numerical
results that electron fluids near the central conductor are tied to an external
toroidal field and ion fluids are not. The magnetic configurations change from
the high- HD-ST (>1) with paramagnetic toroidal field and low-
(volume average value, ( 2 %) through the
helicity-driven spheromak and RFP to the ultra low- HD-ST (0<q<1) with
diagmagnetic toroidal field and high- ($\beta\approx 18\%) as the
external toroidal field at the inner edge region decreases and reverses the
sign. The two-fluid effecs are more significant in this equilibrium transition
when the ion diagmagnetic drift is dominant in the flowing two-fluid.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004,
Nice (France
Fermi Surface Study of Quasi-Two-Dimensional Organic Conductors by Magnetooptical Measurements
Magnetooptical measurements of several quasi-two-dimensional (q2D) organic
conductors, which have simple Fermi surface structure, have been performed by
using a cavity perturbation technique. Despite of the simple Fermi surface
structure, magnetooptical resonance results show a dramatic difference for each
sample. Cyclotron resonances (CR) were observed for q-(BEDT-TTF)2I3 and
(BEDT-TTF)3Br(pBIB), while periodic orbit resonances (POR) were observed for
(BEDT-TTF)2Br(DIA) and (BEDT-TTF)3Cl(DFBIB). The selection of the resonance
seems to correspond with the skin depth for each sample. The effective mass of
POR seems to have a mass enhancement due to the many-body effect, while
effective mass of CR is independent of the strength of the electron-electron
interaction. The scattering time deduced from each resonance's linewidth will
be also presented.Comment: 10 pages, 8 figures, to be published to J. Phys. Soc. Jpn Vol.72 No.1
(accepted
Theory of Thermoelectric Power in High-Tc Superconductors
We present a microscopic theory for the thermoelectric power (TEP) in high-Tc
cuprates. Based on the general expression for the TEP, we perform the
calculation of the TEP for a square lattice Hubbard model including all the
vertex corrections necessary to satisfy the conservation laws. In the present
study, characteristic anomalous temperature and doping dependences of the TEP
in high-Tc cuprates, which have been a long-standing problem of high-Tc
cuprates, are well reproduced for both hole- and electron-doped systems, except
for the heavily under-doped case. According to the present analysis, the strong
momentum and energy dependences of the self-energy due to the strong
antiferromagnetic fluctuations play an essential role in reproducing
experimental anomalies of the TEP.Comment: 5 pages, 8 figures, to appear in J. Phys. Soc. Jpn. 70 (2001) No.10.
Figure 2 has been revise
Evolution of Hall coefficient in two-dimensional heavy fermion CeCoIn
We report on the pressure dependence of the Hall coefficient in
quasi-2D heavy fermion CeCoIn. At ambient pressure, below a temperature
associated with the emergence of non-Fermi liquid properties, is
anomalously enhanced. We found that the restoration of the Fermi liquid state
with applied pressure leads to a gradual suppression of this dramatic
enhancement. Moreover, the enhancement in was found to be confined to an
intermediate temperature window, where inelastic electron-electron scattering
is dominant. Our results strongly support the presence of cold and hot spots on
the Fermi surface probably due to anisotropic scattering by antiferromagnetic
fluctuations, which may also prove relevant for the debate on the anomalous
normal-state properties of high- cuprates.Comment: 9 pages, 5 fiqures, to be published in J. Phys. Soc. Jp
Electrical Conductivity of Fermi Liquids. I. Many-body Effect on the Drude Weight
On the basis of the Fermi liquid theory, we investigate the many-body effect
on the Drude weight. In a lattice system, the Drude weight is modified by
electron-electron interaction due to Umklapp processes, while it is not
renormalized in a Galilean invariant system. This is explained by showing that
the effective mass for is defined through the current, not
velocity, of quasiparticle. It is shown that the inequality is required
for the stability against the uniform shift of the Fermi surface. The result of
perturbation theory applied for the Hubbard model indicates that as a
function of the density is qualitatively modified around half filling
by Umklapp processes.Comment: 20 pages, 2 figures; J. Phys. Soc. Jpn. Vol.67, No.
Multi-indexed Wilson and Askey-Wilson Polynomials
As the third stage of the project multi-indexed orthogonal polynomials, we
present, in the framework of 'discrete quantum mechanics' with pure imaginary
shifts in one dimension, the multi-indexed Wilson and Askey-Wilson polynomials.
They are obtained from the original Wilson and Askey-Wilson polynomials by
multiple application of the discrete analogue of the Darboux transformations or
the Crum-Krein-Adler deletion of 'virtual state solutions' of type I and II, in
a similar way to the multi-indexed Laguerre, Jacobi and (q-)Racah polynomials
reported earlier.Comment: 30 pages. Three references added. To appear in J.Phys.A. arXiv admin
note: text overlap with arXiv:1203.586
Magnetoresistance in High-Tc Superconductors: The Role of Vertex Corrections
In high-Tc cuprates, the orbital magnetoresistance in plane (MR,
) is anomalously enhanced at lower tempemeratures compared
with conventional Fermi liquids, and thus Kohler's rule is strongly violated.
Moreover, it should be noted that an intimate relation between the MR and the
Hall coefficient (), , holds well
experimentally, and is called the "modified Kohler's rule". In this letter, we
study this long-standing problem in terms of the nearly antiferromagnetic (AF)
Fermi liquid. We analyze the exact expression for the MR by including the
vertex corrections (VC's) to keep the conservation laws, and find the
approximate "scaling relation"
( being the AF correlation length.) in the presence of AF
fluctuations. The factor , which comes from the VC's for the
current, gives the additional temperature dependence. By taking account of the
relation [Kontani et al., PRB 59 (1999) 14723.], we
can naturally explain the modified Kohler's rule. In conclusion, based on the
Fermi liquid theory, the famous {\it seemingly} non-Fermi liquid behaviors of
the Hall coefficient and the MR in high-Tc cuprates are naturally understood on
an equal footing.Comment: 5 pages, 5 figures, to appear in J. Phys. Soc. Jpn. 70 (2001) No.
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