14,422 research outputs found
Transient localization in crystalline organic semiconductors
A relation derived from the Kubo formula shows that optical conductivity
measurements below the gap frequency in doped semiconductors can be used to
probe directly the time-dependent quantum dynamics of charge carriers. This
allows to extract fundamental quantities such as the elastic and inelastic
scattering rates, as well as the localization length in disordered systems.
When applied to crystalline organic semiconductors, an incipient electron
localization caused by large dynamical lattice disorder is unveiled, implying a
breakdown of semiclassical transport.Comment: Revised version, to appear in Phys. Rev. B Rapid Communication
Sublattice Asymmetric Reductions of Spin Values on Stacked Triangular Lattice Antiferromagnet CsCoBr
We study the reductions of spin values of the ground state on a stacked
triangular antiferromagnet using the spin-wave approach. We find that the spin
reductions have sublattice asymmetry due to the cancellation of the molecular
field. The sublattice asymmetry qualitatively analyzes the NMR results of
CsCoBr.Comment: 5pages, 5figure
Variations on the Supersymmetric Q6 Model of Flavor
We observe that a recently proposed supersymmetric model with Q6 flavor
symmetry admits a new CP violating ground state. A new sum rule for the quark
mixing parameters emerges, which is found to be consistent with data. Simple
extensions of the model to the neutrino sector suggest an inverted hierarchical
mass spectrum with nearly maximal CP violation (|delta_{MNS}| simeq pi/2).
Besides reducing the number of parameters in the fermion sector, these models
also provide solutions to the SUSY flavor problem and the SUSY CP problem. We
construct a renormalizable scalar potential that leads to the spontaneous
breaking of CP symmetry and the family symmetry.Comment: 22 pages, 7 figure
Steps and dips in the ac conductance and noise of mesoscopic structures
The frequency dependence of the equilibrium ac conductance (or the noise
power spectrum) through a mesoscopic structure is shown to exhibit steps and
dips. The steps, at energies related to the resonances of the structure, are
closely related to the partial Friedel phases of these resonances, thus
allowing a direct measurement of these phases (without interferometry). The
dips in the spectrum are related to a destructive interference in the
absorption of energy by transitions between these resonances, in some
similarity with the Fano effect.Comment: 4 pages, 2 figure
Photon Statistics for Single Molecule Non-Linear Spectroscopy
We consider the theory of the non-linear spectroscopy for a single molecule
undergoing stochastic dynamics and interacting with a sequence of two laser
pulses. General expressions for photon counting statistics are obtained, and an
exact solution to the problem of the Kubo-Anderson process is found. In the
limit of impulsive pulses the information on the photon statistics is contained
in the molecule's dipole correlation function. The selective limit where
temporal resolution is maintained, the semi-classical approximation and the
fast modulation limit exhibit general behaviors of this new type of
spectroscopy. We show how the design of the external field leads to rich
insights on dynamics of individual molecules which are different than those
found for an ensemble
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