An Anderson-Fano Resonance and Shake-Up Processes in the Magneto-Photoluminescence of a Two-Dimensional Electron System

We report an anomalous doublet structure and low-energy satellite in the magneto-photoluminescence spectra of a two-dimensional electron system. The doublet structure moves to higher energy with increasing magnetic field and is most prominent at odd filling factors 5 and 3. The lower-energy satellite peak tunes to lower energy for increasing magnetic field between filling factor 6 and 2. These features occur at energies below the fundamental band of recombination originating from the lowest Landau level and display striking magnetic field and temperature dependence that indicates a many-body origin. Drawing on a recent theoretical description of Hawrylak and Potemski, we show that distinct mechanisms are responsible for each feature.Comment: 14 pages including 5 figures. To appear in the April 15th edition of Phy. Rev. B. rapid com

Multiband theory of multi-exciton complexes in self-assembled quantum dots

We report on a multiband microscopic theory of many-exciton complexes in self-assembled quantum dots. The single particle states are obtained by three methods: single-band effective-mass approximation, the multiband $k\cdot p$ method, and the tight-binding method. The electronic structure calculations are coupled with strain calculations via Bir-Pikus Hamiltonian. The many-body wave functions of $N$ electrons and $N$ valence holes are expanded in the basis of Slater determinants. The Coulomb matrix elements are evaluated using statically screened interaction for the three different sets of single particle states and the correlated $N$-exciton states are obtained by the configuration interaction method. The theory is applied to the excitonic recombination spectrum in InAs/GaAs self-assembled quantum dots. The results of the single-band effective-mass approximation are successfully compared with those obtained by using the of $k\cdot p$ and tight-binding methods.Comment: 10 pages, 8 figure

Tunneling effects on impurity spectral function in coupled asymmetric quantum wires

The impurity spectral function is studied in coupled double quantum wires at finite temperatures. Simple anisotropy in the confinement direction of the wires leads to finite non-diagonal elements of the impurity spectral function matrix. These non-diagonal elements are responsible for tunneling effects and result in pronounced extra peak in the impurity spectral function up to temperatures as high as 20 K.Comment: Accepted in Phys. Rev.

Solution of the X-ray edge problem for 2D electrons in a magnetic field

The absorption and emission spectra of transitions between a localized level and a two-dimensional electron gas, subjected to a weak magnetic field, are calculated analytically. Adopting the Landau level bosonization technique developed in previous papers, we find an exact expression for the relative intensities of spectral lines. Their envelope function, governed by the interaction between the electron gas and the core hole, is reminescent of the famous Fermi edge singularity, which is recovered in the limit of a vanishing magnetic field.Comment: 4 pages, 1 figur

Analytic results for NN particles with 1/r21/r^2 interaction in two dimensions and an external magnetic field

The $2N$-dimensional quantum problem of $N$ particles (e.g. electrons) with interaction $\beta/r^2$ in a two-dimensional parabolic potential $\omega_0$ (e.g. quantum dot) and magnetic field $B$, reduces exactly to solving a $(2N-4)$-dimensional problem which is independent of $B$ and $\omega_0$. An exact, infinite set of relative mode excitations are obtained for any $N$. The $N=3$ problem reduces to that of a ficticious particle in a two-dimensional, non-linear potential of strength $\beta$, subject to a ficticious magnetic field $B_{\rm fic}\propto J$, the relative angular momentum.Comment: To appear in Physical Review Letters (in press). RevTeX file. Two figures available from [email protected] or [email protected]

Voltage-tunable singlet-triplet transition in lateral quantum dots

Results of calculations and high source-drain transport measurements are presented which demonstrate voltage-tunable entanglement of electron pairs in lateral quantum dots. At a fixed magnetic field, the application of a judiciously-chosen gate voltage alters the ground-state of an electron pair from an entagled spin singlet to a spin triplet.Comment: 8.2 double-column pages, 10 eps figure

Theory of electronic transport through a triple quantum dot in the presence of magnetic field

Theory of electronic transport through a triangular triple quantum dot subject to a perpendicular magnetic field is developed using a tight binding model. We show that magnetic field allows to engineer degeneracies in the triple quantum dot energy spectrum. The degeneracies lead to zero electronic transmission and sharp dips in the current whenever a pair of degenerate states lies between the chemical potential of the two leads. These dips can occur with a periodicity of one flux quantum if only two levels contribute to the current or with half flux quantum if the three levels of the triple dot contribute. The effect of strong bias voltage and different lead-to-dot connections on Aharonov-Bohm oscillations in the conductance is also discussed

Correlated few-electron states in vertical double-quantum-dot systems

The electronic properties of semiconductor, vertical, double quantum dot systems with few electrons are investigated by means of analytic, configuration-interaction, and mean-field methods. The combined effect of a high magnetic field, electrostatic confinement, and inter-dot coupling, induces a new class of few-electron ground states absent in single quantum dots. In particular, the role played by the isospin (or quantum dot index) in determining the appearance of new ground states is analyzed and compared with the role played by the standard spin.Comment: 20 pages, Latex, figures upon request. To appear in Phys. Rev. B (January 1995

Quantum Dot Version of Berry's Phase: Half-Integer Orbital Angular Momenta

We show that Berry's geometrical (topological) phase for circular quantum dots with an odd number of electrons is equal to \pi and that eigenvalues of the orbital angular momentum run over half-integer values. The non-zero value of the Berry's phase is provided by axial symmetry and two-dimensionality of the system. Its particular value (\pi) is fixed by the Pauli exclusion principle. Our conclusions agree with the experimental results of T. Schmidt {\it at el}, \PR B {\bf 51}, 5570 (1995), which can be considered as the first experimental evidence for the existence of a new realization of Berry's phase and half-integer values of the orbital angular momentum in a system of an odd number of electrons in circular quantum dots.Comment: 4 pages, 2 figure

Coulomb blockade of tunnelling through compressible rings formed around an antidot: an explanation for h/2eh/2e Aharonov-Bohm oscillations

We consider single-electron tunnelling through antidot states using a Coulomb-blockade model, and give an explanation for h/2e Aharonov-Bohm oscillations, which are observed experimentally when the two spins of the lowest Landau level form bound states. We show that the edge channels may contain compressible regions, and using simple electrostatics, that the resonance through the outer spin states should occur twice per h/e period. An antidot may be a powerful tool for investigating quantum Hall edge states in general, and the interplay of spin and charging effects that occurs in quantum dots.Comment: 5 pages, 4 Postscript figure