We report the Coulomb mediated hybridization of excitonic states in an optically active, artificial quantum dot molecule. By probing the optical response of the artificial molecule as a function of the static electric field applied along the molecular axis, we observe unexpected avoided level crossings that do not arise from the dominant single particle tunnel coupling. We identify a new few-particle coupling mechanism stemming from Coulomb interactions between different neutral exciton states. Such Coulomb resonances hybridize the exciton wave function over four different electron and hole single-particle orbitals. Comparisons of experimental observations with microscopic 8-band k · p calculations taking into account a realistic quantum dot geometry show good agreement and reveal that the Coulomb resonances arise from broken symmetry in the artificial molecule.Understanding and controlling the fundamental interactions that couple discrete quantum states lies at the very heart of applied quantum science. For example, couplings between distinct physical subsystems mediated by the Coulomb interaction can be used to entangle qubits electrostatically [1], to build single-photon transistors on the basis of Förster resonances [2] or to control resonant energy transfer [3]. Strong tunnel couplings between proximal quantum dots have been shown to facilitate electrical and optical spin-qubit operations [4,5] while long range magnetic dipolar interactions have been exploited for prototype quantum registers [6]. Thus the nature of quantum couplings has been under extensive investigation for many prototypical quantum systems. Examples include naturally occurring atoms [3,7,8] and defect centers [9,10] as well as artificial atoms and molecules [11][12][13]. Due to advanced nanostructure fabrication techniques [14,15] and efficient coupling to light [16,17], artificial molecules consisting of pairs of semiconductor quantum dots (QDs) have emerged as ideal prototypical solid-state systems to investigate and electrically control interactions between proximal quantum systems [11,12].By embedding a QD-molecule into the intrinsic region of a diode structure, exciton states in the different QDs can be tuned into and out of resonance by controlling the electric field along the growth direction [11,12]. The fundamental signatures of quantum couplings are avoided level crossings in the electronic energy level structure of a QD-molecule as single particle states are tuned in and out of resonance [18]. The importance of Coulomb interactions has been pointed out for the form and position of resonances in QD-molecule systems [19][20][21]. However, single particle tunneling that either hybridizes single electrons or holes remains the dominant coupling mechanism in these cases [11][12][13][22][23][24][25]. Most recently another resonant coupling mechanism with an inherently two particle nature has been predicted theoretically that entirely relies on the Coulomb mediated interaction between two different exciton states [26]. In strong contra...

The interest in enantioseparation and enantiopurification of chiral molecules has been drastically increasing over the past decades,since these are important steps in various disciplines such as pharmaceutical industry,asymmetric catalysis,a nd chiral sensing.B ye xposing racemic samples of BINOL (1,1'-bi-2-naphthol) coated onto achiral glass substrates to circularly polarized light, we unambiguously demonstrate that by controlling the handedness of circularly polarized light, preferential desorption of enantiomers can be achieved. There are currently no mechanisms knownt hat would describe this phenomenon. Our observation together with as implified phenomenological model suggests that the process of laser desorption needs to be further developed and the contribution of quantum mechanical processes should be revisited to account for these data. Asymmetric laser desorption provides us with ac ontamination-free technique for the enantioenrichment of chiral compounds.

The interest in enantioseparation and enantiopurification of chiral molecules has been drastically increasing over the past decades,since these are important steps in various disciplines such as pharmaceutical industry,asymmetric catalysis,a nd chiral sensing.B ye xposing racemic samples of BINOL (1,1'-bi-2-naphthol) coated onto achiral glass substrates to circularly polarized light, we unambiguously demonstrate that by controlling the handedness of circularly polarized light, preferential desorption of enantiomers can be achieved. There are currently no mechanisms knownt hat would describe this phenomenon. Our observation together with as implified phenomenological model suggests that the process of laser desorption needs to be further developed and the contribution of quantum mechanical processes should be revisited to account for these data. Asymmetric laser desorption provides us with ac ontamination-free technique for the enantioenrichment of chiral compounds.

The photophysical properties of three 3-diethylphosphonocoumarin derivatives are studied by transient absorption spectroscopy and DFT calculations.