9,229 research outputs found
Electron Band Structure in a Two Dimensional Periodic Magnetic Field
In this paper we study the energy spectrum of a two dimensional electron gas
(2DEG) in a two dimensional periodic magnetic field. Both a square magnetic
lattice and a triangular one are considered. We consider the general case where
the magnetic field in a cell can be of any shape. A general feature of the band
structure is bandwidth oscillation as a function of the Landau index. A
triangular magnetic lattice on a 2DEG can be realized by the vortex lattice of
a superconductor film coated on top of a heterojunction. Our calculation
indicates a way of relating the energy spectrum of the 2DEG to the vortex
structure. We have also derived conditions under which the effects of a weak
magnetic modulation, periodic or not, may be reproduced by an electric
potential modulation, and vice versa.Comment: 16 pages in TeX and 5 uuencoded figure
Anomalous Nernst and Hall effects in magnetized platinum and palladium
We study the anomalous Nernst effect (ANE) and anomalous Hall effect (AHE) in
proximity-induced ferromagnetic palladium and platinum which is widely used in
spintronics, within the Berry phase formalism based on the relativistic band
structure calculations. We find that both the anomalous Hall ()
and Nernst () conductivities can be related to the spin Hall
conductivity () and band exchange-splitting () by
relations and
,
respectively. In particular, these relations would predict that the
in the magnetized Pt (Pd) would be positive (negative) since
the is positive (negative). Furthermore, both
and are approximately proportional to the
induced spin magnetic moment () because the is a linear
function of . Using the reported in the magnetized Pt and Pd, we
predict that the intrinsic anomalous Nernst conductivity (ANC) in the magnetic
platinum and palladium would be gigantic, being up to ten times larger than,
e.g., iron, while the intrinsic anomalous Hall conductivity (AHC) would also be
significant.Comment: Accepted for publication in the Physical Review
Study on QoS support in 802.11e-based multi-hop vehicular wireless ad hoc networks
Multimedia communications over vehicular ad hoc networks (VANET) will play an important role in the future intelligent transport system (ITS). QoS support for VANET therefore becomes an essential problem. In this paper, we first study the QoS performance in multi-hop VANET by using the standard IEEE 802.11e EDCA MAC and our proposed triple-constraint QoS routing protocol, Delay-Reliability-Hop (DeReHQ). In particular, we evaluate the DeReHQ protocol together with EDCA in highway and urban areas. Simulation results show that end-to-end delay performance can sometimes be achieved when both 802.11e EDCA and DeReHQ extended AODV are used. However, further studies on cross-layer optimization for QoS support in multi-hop environment are required
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