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 CsCoBr3_3

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$_3$.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