Correlation Effects in Quantum Dot Wave Function Imaging

We demonstrate that in semiconductor quantum dots wave functions probed by imaging techniques based on local tunneling spectroscopies like STM show characteristic signatures of electron-electron Coulomb correlation. We predict that such images correspond to ``quasi-particle'' wave functions which cannot be computed by standard mean-field techniques (density functional theory, Hartree-Fock) in the strongly correlated regime corresponding to low electron density. From the configuration-interaction solution of the few-particle problem for prototype dots, we find that quasi-particle wave function images may display signatures of Wigner crystallization.Comment: Latex 2e + jjap2 style version 1.0. 4 pages, 3 postscript figures. Submitted to the Japanese Journal of Applied Physics as Proceeding of STM05 Conference, Sapporo, Japan, July 3-8, 200

Optical near-field mapping of excitons and biexcitons in naturally occurring semiconductor quantum dots

We calculate the near-field optical spectra of excitons and biexcitons in semiconductor quantum dots naturally occurring at interface fluctuations in GaAs-based quantum wells, using a non-local description of the response function to a spatially modulated electro-magnetic field. The relative intensity of the lowest, far-field forbidden excitonic states is predicted; the spatial extension of the ground biexciton state is found in agreement with recently published experiments

Electron-hole localization in coupled quantum dots

We theoretically investigate correlated electron-hole states in vertically coupled quantum dots. Employing a prototypical double-dot confinement and a configuration-interaction description for the electron-hole states, it is shown that the few-particle ground state undergoes transitions between different quantum states as a function of the interdot distance, resulting in unexpected spatial correlations among carriers and in electron-hole localization. Such transitions provide a direct manifestations of inter- and intradot correlations, which can be directly monitored in experiments.Comment: 11 pages, 3 figures (eps), LaTeX 2e. To appear in PRB (Rapid Communication

Quantum interference in nanometric devices: ballistic transport across arrays of T-shaped quantum wires

We propose that the recently realized T-shaped semiconductor quantum wires (T-wires) could be exploited as three-terminal quantum interference devices. T-wires are formed by intersecting two quantum wells (QWs). By use of a scattering matrix approach and the Landauer-B\"uttiker theory, we calculate the conductance for ballistic transport in the parent QWs and across the wire region as a function of the injection energy. We show that different conductance profiles can be selected by tailoring the widths of the QWs and/or combining more wires on the scale of the Fermi wavelength. Finally, we discuss the possibility of obtaining spin-dependent conductance of ballistic holes in the same structures.Comment: To appear in the 09/15/97 issue of Appl. Phys. Lett. (9 pages in REVTEX + 2 figures in postscript

Addition energies in semiconductor quantum dots: Role of electron-electron interaction

We show that the addition spectra of semiconductor quantum dots in the presence of magnetic field can be studied through a theoretical scheme that allows an accurate and practical treatment of the single particle states and electron-electron interaction up to large numbers of electrons. The calculated addition spectra exhibit the typical structures of Hund-like shell filling, and account for recent experimental findings. A full three dimensional description of Coulomb interaction is found to be essential for predicting the conductance characteristics of few-electron semiconductor structures.Comment: LaTeX 2.09, RevTeX, 3 pages, 3 Postscript figure

Field-controlled suppression of phonon-induced transitions in coupled quantum dots

We calculate the longitudinal-acoustic phonon scattering rate for a vertical double quantum dot system with weak lateral confinement and show that a strong modulation of the single-electron excited states lifetime can be induced by an external magnetic or electric field. The results are obtained for typical realistic devices using a Fermi golden rule approach and a three-dimensional description of the electronic quantum states.Comment: REVTex4 class, 6 pages, 3 figures, to be published in Applied Physics Letter

High-finesse optical quantum gates for electron spins in artificial molecules

A doped semiconductor double-quantum-dot molecule is proposed as a qubit realization. The quantum information is encoded in the electron spin, thus benefiting from the long relevant decoherence times; the enhanced flexibility of the molecular structure allows to map the spin degrees of freedom onto the orbital ones and vice versa, and opens the possibility for high-finesse (conditional and unconditional) quantum gates by means of stimulated Raman adiabatic passage.Comment: To appear in Phys. Rev. Let