11,683 research outputs found
Determining the Supernova Direction by its Neutrinos
Supernova neutrinos, which arrive at Earth earlier than light, allow for the
earliest determination of the direction of the supernova. The topic of this
paper is to study how accurately we can determine the supernova direction. We
simulate supernova neutrino events at the SuperKamiokande detector, using a
realistic supernova model and several realistic neutrino oscillation models.
With the results of our simulation, we can restrict the supernova direction to
be within a circle of radius . In several neutrino oscillation models,
this accuracy is increased to . We also discuss the influence of an
accident that occurred at the SuperKamiokande detector. After repair of the
detector, using the remaining PMTs, the accuracy becomes about for
no oscillation.Comment: 20 pages, 8 figures, Prog. Theor. Phys., accepte
Origin of the anomalous magnetic circular dichroism spectral shape in ferromagnetic (Ga,Mn)As: Impurity bands inside the band gap
The electronic structure of a prototype dilute magnetic semiconductor (DMS),
Ga1-xMnxAs, is studied by magnetic circular dichroism (MCD) spectroscopy. We
prove that the optical transitions originated from impurity bands cause the
strong positive MCD background. The MCD signal due to the E0 transition from
the valence band to the conduction band is negative indicating that the p-d
exchange interactions between the p-carriers and d-spin is antiferromagnetic.
The negative E0 MCD signal also indicates that the hole-doping of the valence
band is not so large as previously assumed. The impurity bands seem to play
important roles for the ferromagnetism of Ga1-xMnxAs.Comment: 13 pages, 3 figure
Magneto-optical properties of multilayer graphenes
The magneto-optical absorption properties of graphene multilayers are
theoretically studied. It is shown that the spectrum can be decomposed into
sub-components effectively identical to the monolayer or bilayer graphene,
allowing us to understand the spectrum systematically as a function of the
layer number. Odd-layered graphenes always exhibit absorption peaks which
shifts in proportion to sqrt(B), with B being the magnetic field, due to the
existence of an effective monolayer-like subband. We propose a possibility of
observing the monolayer-like spectrum even in a mixture of multilayer graphene
films with various layers numbers.Comment: 9 pages, 7 figure
Zn-doping effect on the magnetotransport properties of Bi_{2}Sr_{2-x}La_{x}CuO_{6+\delta} single crystals
We report the magnetotransport properties of
Bi_{2}Sr_{2-x}La_{x}Cu_{1-z}Zn_{z}O_{6+\delta} (Zn-doped BSLCO) single crystals
with z of up to 2.2%. Besides the typical Zn-doping effects on the in-plane
resistivity and the Hall angle, we demonstrate that the nature of the
low-temperature normal state in the Zn-doped samples is significantly altered
from that in the pristine samples under high magnetic fields. In particular, we
observe nearly-isotropic negative magnetoresistance as well as an increase in
the Hall coefficient at very low temperatures in non-superconducting Zn-doped
samples, which we propose to be caused by the Kondo scattering from the local
moments induced by Zn impurities.Comment: 4 pages, 4 figures, final version (one reference added), published in
Phys. Rev.
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