All-organic-based photovoltaic solar cells have attracted considerable attention because of their low-cost processing and short energy payback time. In such systems the primary dissociation of an optical excitation into a pair of photocarriers has been recently shown to be extremely rapid and efficient, but the physical reason for this remains unclear. Here, two-dimensional photocurrent excitat...

We theoretically investigate coherent optical spectroscopy of a biological semiconductor quantum dot (QD) coupled to DNA molecules. Coupling with DNAs, the linear optical responses of the peptide QDs will be enhanced significantly in the simultaneous presence of two optical fields. Based on this technique, we propose a scheme to measure the vibrational frequency of DNA and the coupling strength...

We measured the low-lying crystal field levels of Nd3+ in Nd3Ga5SiO14 via magneto-optical spectroscopy and employed the extracted energies, magnetic moments, and symmetries to analyze the magnetic properties and test the spin liquid candidacy of this material. The exchange interaction is surprisingly small, a discovery that places severe constraints on models used to describe the ground state o...

Previous second-harmonic-generation experiments on metallic split-ring-resonator arrays have been performed at fixed fundamental laser center frequency. Here, we perform nonlinear optical spectroscopy on a first set of samples, revealing pronounced resonances. Furthermore, to clarify the role of higher-order split-ring resonances, we perform additional experiments on a second set of samples in ...

We performed optical spectroscopy measurement on single crystals of BaFe2As2 and SrFe2As2, the parent compounds of FeAs-based superconductors. Both are found to be quite metallic with fairly large plasma frequencies at high temperature. Upon entering the spin-density-wave state, the formation of partial energy gaps was clearly observed with the surprising presence of two different energy scales...

Transient four-wave mixing experiments with 100 fs pulses in a dense potassium vapor probe the electronic energy fluctuations that lead to optical decoherence. Echo-peak shift experiments yield a biexponential two-time correlation function of energy level fluctuations. Molecular dynamics simulations show that the slow component is a many-body excitonic contribution arising from long-range reson...

We report on the energy- and momentum-resolved optical response of black phosphorus (BP) in its bulk form. Along the armchair direction of the puckered layers, we find a highly dispersive mode that is strongly suppressed in the perpendicular (zigzag) direction. This mode emerges out of the single-particle continuum for finite values of momentum and is therefore interpreted as an exciton. We arg...

The correlation between coherent driving and non-Markovian dissipation plays a vital role in optical processes. To exhibit its effect on the simulation of optical spectroscopy, we explore the correlated driving-dissipation equation (CODDE) [R. X. Xu and Y. J. Yan, J. Chem. Phys. 116, 9196 (2002)], which modifies the conventional Redfield theory with the inclusion of correlated driving-dissipati...

We describe further observations of QSO J0906+6930, a z=5.48 blazar likely to be detected in γ-rays. New radio and X-ray data place significant constraints on any kpc-scale extension of the VLBA-detected jet. Improved optical spectroscopy detects absorption from an intervening galaxy at z=1.849 and raise the possibility that this distant, bright source is lensed. We combine the new data into an...