Photoassociation adiabatic passage of ultracold Rb atoms to form ultracold Rb_2 molecules

We theoretically explore photoassociation by Adiabatic Passage of two colliding cold ^{85}Rb atoms in an atomic trap to form an ultracold Rb_2 molecule. We consider the incoherent thermal nature of the scattering process in a trap and show that coherent manipulations of the atomic ensemble, such as adiabatic passage, are feasible if performed within the coherence time window dictated by the temperature, which is relatively long for cold atoms. We show that a sequence of ~2*10^7 pulses of moderate intensities, each lasting ~750 ns, can photoassociate a large fraction of the atomic ensemble at temperature of 100 microkelvin and density of 10^{11} atoms/cm^3. Use of multiple pulse sequences makes it possible to populate the ground vibrational state. Employing spontaneous decay from a selected excited state, one can accumulate the molecules in a narrow distribution of vibrational states in the ground electronic potential. Alternatively, by removing the created molecules from the beam path between pulse sets, one can create a low-density ensemble of molecules in their ground ro-vibrational state.Comment: RevTex, 23 pages, 9 figure

Incomplete Photonic Bandgap as Inferred from the Speckle Pattern of Scattered Light Waves

Motivated by recent experiments on intensity correlations of the waves transmitted through disordered media, we demonstrate that the speckle pattern from disordered photonic crystal with incomplete band-gap represents a sensitive tool for determination the stop-band width. We establish the quantitative relation between this width and the {\em angualar anisotropy} of the intensity correlation function.Comment: 6 pages, 3 figure

Expansion of a Bose-Einstein Condensate in the Presence of Disorder

Expansion of a Bose-Einstein condensate (BEC) is studied, in the presence of a random potential. The expansion is controlled by a single parameter, $(\mu\tau_{eff} /\hbar)$, where $\mu$ is the chemical potential, prior to the release of the BEC from the trap, and $\tau_{eff}$ is a transport relaxation time which characterizes the strength of the disorder. Repulsive interactions (nonlinearity) facilitate transport and can lead to diffusive spreading of the condensate which, in the absence of interactions, would have remained localized in the vicinity of its initial location

Stimulated Raman Adiabatic Passage (STIRAP) as a Route to Achieving Optical Control in Plasmonics

Optical properties of ensembles of three-level quantum emitters coupled to plasmonic systems are investigated employing a self-consistent model. It is shown that stimulated Raman adiabatic passage (STIRAP) technique can be successfully adopted to control optical properties of hybrid materials with collective effects present and playing an important role in light-matter interactions. We consider a core-shell nanowire comprised of a silver core and a shell of coupled quantum emitters and utilize STIRAP scheme to control scattering efficiency of such a system in a frequency and spatial dependent manner. After the STIRAP induced population transfer to the final state takes place, the core-shell nanowire exhibits two sets of Rabi splittings with Fano lineshapes indicating strong interactions between two different atomic transitions driven by plasmon near-fields.Comment: 11 pages, 6 figures, accepted, Physical Review

Pulse-Bandwidth Dependence of Coherent Phase Control of Resonance-Mediated (2+1) Three-Photon Absorption

We study in detail coherent phase control of femtosecond resonance-mediated (2+1) three-photon absorption and its dependence on the spectral bandwidth of the excitation pulse. The regime is the weak-field regime of third perturbative order. The corresponding interference mechanism involves a group of three-photon excitation pathways that are on resonance with the intermediate state and a group of three-photon excitation pathways that are near resonant with it. The model system of the study is atomic sodium (Na), for which experimental and numerical-theoretical results are obtained. Prominent among the results is our finding that with simple proper pulse shaping an increase in the excitation bandwidth leads to a corresponding increase in the enhancement of the three-photon absorption over the absorption induced by the (unshaped) transform-limited pulse. For example, here, a 40-nm bandwidth leads to an order-of-magnitude enhancement over the transform-limited absorption.Comment: 23 pages, 5 figure

Heat capacity of the site-diluted spin dimer system Ba3(Mn1-xVx)2O8

Heat capacity and susceptibility measurements have been performed on the diluted spin dimer compound Ba3(Mn1-xVx)2O8. The parent compound Ba3Mn2O8 is a spin dimer system based on pairs of antiferromagnetically coupled S = 1, 3d2 Mn5+ ions such that the zero field groundstate is a product of singlets. Substitution of non-magnetic S = 0, 3d0 V5+ ions leads to an interacting network of unpaired Mn moments, the low temperature properties of which are explored in the limit of small concentrations, 0<x<0.05. The zero-field heat capacity of this diluted system reveals a progressive removal of magnetic entropy over an extended range of temperatures, with no evidence for a phase transition. The concentration dependence does not conform to expectations for a spin glass state. Rather, the data suggest a low temperature random singlet phase, reflecting the hierarchy of exchange energies found in this system.Comment: Full Publication Citation Include