593 research outputs found
Dynamical scaling analysis of the optical Hall conductivity in the quantum Hall regime
Dynamical scaling analysis is theoretically performed for the ac (optical)
Hall conductivity as a function of Fermi
energy and frequency for the two-dimensional electron
gas and for graphene. In both systems, results based on exact diagonalization
show that displays a well-defined dynamical
scaling, for which the dynamical critical exponent as well as the localization
exponent are fitted and plugged in. A crossover from the dc-like bahavior to
the ac regime is identified. The dynamical scaling analysis has enabled us to
quantify the plateau in the ac Hall conductivity previously obtained, and to
predict that the plateaux structure in ac is robust enough to be observed in
the THz regime.Comment: 5 pages, 3 figure
Faraday rotation in bilayer and trilayer graphene in the quantum Hall regime
Optical Hall conductivity, as directly related to Faraday rotation, is
theoretically studied for bilayer and trilayer graphene. In bilayer graphene,
the trigonal warping of the band dispersion greatly affects the resonance
structures in Faraday rotation not only in the low-energy region where small
Dirac cones emerge, but also in the higher-energy parabolic bands as a sequence
of satellite resonances. In ABA-stacked trilayer, the resonance spectrum is a
superposition of effective monolayer and bilayer contributions with band gaps,
while ABC trilayer exhibits a distinct spectrum peculiar to the cubic-dispersed
bands with a strong trigonal warping, where the signals associated with
low-energy Dirac cones should be directly observable owing to a large Lifshitz
transition energy ().Comment: 10 pages, 7 figure
Isolation of a transcriptionally active element of high copy number retrotransposons in sweetpotato genome
Many plant retrotransposons have been characterized, but only three families (Tnt1, Tto1 and
Tos17) have been demonstrated to be transpositionally competent. We followed a novel approach
that enabled us to identify an active element of the Ty1-copia retrotransposon family with
estimated 400 copies in the sweetpotato genome. DNA sequences of Ty1 -copia reverse
transcriptase (RTase) from the sweetpotato genome were analyzed, and a group of
retrotransposon copies probably formed by recent transposition events was further analyzed.
3’RACE on callus cDNA amplified transcripts containing long terminal repeats (LTR) of this
group. The sequence -specific amplification polymorphism (S-SAP) patterns of the LTR sequence
in the genomic DNA were compared between a normal plant and callus lines derived from it. A
callus -specific S-SAP product was found into which the retrotransposon detected by the 3’RACE
had been transposed apparently during cell culture. We conclude that our approach provides an
effective way to identify active elements of retrotransposons with high copy numbers.</p
Two parameter flow of \sigma_{xx}(\omega) - \sigma_{xy}(\omega) for the graphene quantum Hall system in ac regime
Flow diagram of in finite-frequency ()
regime is numerically studied for graphene quantum Hall effect (QHE) system.
The ac flow diagrams turn out to show qualitatively similar behavior as the dc
flow diagrams, which can be understood that the dynamical length scale
determined by the frequency poses a relevant cutoff for the renormalization
flow. Then the two parameter flow is discussed in terms of the dynamical
scaling theory. We also discuss the larger- regime which exhibits
classical flows driven by the raw frequency .Comment: 6 pages, 4 figure
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