Archivio della ricerca dell'Università di Modena e Reggio Emiliahttps://iris.unimore.itIl sistema di repository digitale IRIS acquisisce, archivia, indicizza, conserva e rende accessibili prodotti digitali della ricerca.Sun, 18 Aug 2019 13:33:47 GMT2019-08-18T13:33:47Z10171Probing collective modes of correlated states of few electrons in semiconductor quantum dotshttp://hdl.handle.net/11380/617275Titolo: Probing collective modes of correlated states of few electrons in semiconductor quantum dots
Abstract: Low-lying collective excitations above highly correlated ground states of few interacting electrons confined in GaAs semiconductor quantum dots are probed by resonant inelastic light scattering. We highlight that separate studies of the changes in the spin and charge degrees of freedom offer unique access to the fundamental interactions. The case of quantum dots with four electrons is found to be determined by a competition between triplet and singlet ground states that is uncovered in the rich light scattering spectra of spin excitations. These light scattering results are described within a configuration-interaction framework that captures the role of electron correlation with quantitative accuracy. Recent light scattering results that reveal the impact of anisotropic confining potentials in laterally coupled quantum dots are also reviewed. In these studies, inelastic light scattering methods emerge as powerful probes of collective phenomena and spin configurations in quantum dots with few electrons. (C) 2009 Elsevier Ltd. All rights reserved.
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/11380/6172752009-01-01T00:00:00ZThree interacting atoms in a one-dimensional trap: A benchmark system for computational approacheshttp://hdl.handle.net/11380/1077505Titolo: Three interacting atoms in a one-dimensional trap: A benchmark system for computational approaches
Abstract: We provide an accurate calculation of the energy spectrum of
three atoms interacting through a contact force in a one-dimensional harmonic
trap, considering both spinful fermions and spinless bosons. We use fermionic
energies as a benchmark for exact-diagonalization technique (also known as full
configuration interaction), which is found to slowly converge in the case of strong
interatomic attraction.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/11380/10775052014-01-01T00:00:00ZQuantum phases in artificial moleculeshttp://hdl.handle.net/11380/6445Titolo: Quantum phases in artificial molecules
Abstract: The few-particle state of carriers confined in a quantum dot is controlled by the balance between their kinetic energy and their Coulomb correlation. In coupled quantum dots, both can be tuned by varying the inter-dot tunneling and interactions. Using a theoretical approach based on the diagonalization of the exact Hamiltonian, we show that the transitions between different quantum phases can be induced through the inter-dot coupling both for a system of few electrons (or holes) and for aggregates of electrons and holes. We discuss their manifestations, in addition energy spectra (accessible through capacitance or transport experiments) and optical spectra. (C) 2001 Elsevier Science Ltd. All rights reserved.
Mon, 01 Jan 2001 00:00:00 GMThttp://hdl.handle.net/11380/64452001-01-01T00:00:00ZField-controlled suppression of phonon-induced transitions in coupled quantum dotshttp://hdl.handle.net/11380/454995Titolo: Field-controlled suppression of phonon-induced transitions in coupled quantum dots
Abstract: We suggest that order-of-magnitude reduction of the longitudinal-acoustic phonon scattering rate, the dominant decoherence mechanism in quantum dots, can be achieved in coupled structures by the application of an external electric or magnetic field. Modulation of the scattering rate is traced to the relation between the wavelength of the emitted phonon and the length scale of delocalized electron wave functions. Explicit calculations for realistic devices, performed with a Fermi golden rule approach and a fully three-dimensional description of the electronic quantum states, show that the lifetime of specific states can achieve tens of microseconds. Our findings extend the feasibility basis of many proposals for quantum gates based on coupled quantum dots. (C) 2004 American Institute of Physics.
Thu, 01 Jan 2004 00:00:00 GMThttp://hdl.handle.net/11380/4549952004-01-01T00:00:00ZRaman Signatures of Classical and Quantum Phases in Coupled Dots: a Theoretical Predictionhttp://hdl.handle.net/11380/455007Titolo: Raman Signatures of Classical and Quantum Phases in Coupled Dots: a Theoretical Prediction
Abstract: We study electron molecules in realistic vertically coupled quantum dots in a strong magnetic field. Computing the energy spectrum, pair correlation functions, and dynamical form factor as a function of inter-dot coupling via diagonalization of the many-body Hamiltonian, we identify structural transitions between different phases, some of which do not have a classical counterpart. The calculated Raman cross-section shows how such phases can be experimentally singled out.
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/11380/4550072002-01-01T00:00:00ZImaging quasi-particle wavefunctions in quantum dots in via tunneling spectroscopyhttp://hdl.handle.net/11380/455016Titolo: Imaging quasi-particle wavefunctions in quantum dots in via tunneling spectroscopy
Abstract: We show that in quantum dots the physical quantities probed by local tunneling spectroscopies-namely, the quasiparticle wave functions of interacting electrons-can considerably deviate from their single-particle counterparts as an effect of Coulomb correlation. From the exact solution of the few-particle Hamiltonian for prototype dots, we find that such deviations are crucial to predict wave function images at low electron densities or high magnetic fields.
Sat, 01 Jan 2005 00:00:00 GMThttp://hdl.handle.net/11380/4550162005-01-01T00:00:00ZCorrelation Effects in Wave Function Mapping of Molecular Beam Epitaxy Grown Quantum Dotshttp://hdl.handle.net/11380/737862Titolo: Correlation Effects in Wave Function Mapping of Molecular Beam Epitaxy Grown Quantum Dots
Abstract: We investigate correlation effects in the regime of a few electrons in uncapped InAs quantum dots by tunneling spectroscopy and wave function (WF) mapping at high tunneling currents where electron-electron interactions become relevant. Four clearly resolved states are found, whose approximate symmetries are roughly s and p, in order of increasing energy. Because the major axes of the p-like states coincide, the WF sequence is inconsistent with the imaging of independent-electron orbitals. The results are explained in terms of many-body tunneling theory, by comparing measured maps with those calculated by taking correlation effects into account.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/11380/7378622007-01-01T00:00:00ZImaging correlated wave functions of few-electron quantum dots: theory and STS experimentshttp://hdl.handle.net/11380/421414Titolo: Imaging correlated wave functions of few-electron quantum dots: theory and STS experiments
Abstract: We show both theoretically and experimentally that scanning tunneling spectroscopy (STS) images of semiconductor quantum dots may display clear signatures of electron-electron correlation. We apply many-body tunneling theory to a realistic model, which fully takes into account correlation effects and dot anisotropy. Comparing measured STS images of freestanding InAs quantum dots with those calculated by the full configuration interaction method, we explain the wave-function sequence in terms of images of one- and two-electron states. The STS map corresponding to double charging is significantly distorted by electron correlation with respect to the noninteracting case.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/11380/4214142007-01-01T00:00:00ZEffect of electron-electron interaction on the phonon-mediated spin relaxation in quantum dotshttp://hdl.handle.net/11380/597862Titolo: Effect of electron-electron interaction on the phonon-mediated spin relaxation in quantum dots
Abstract: We estimate the spin relaxation rate due to spin-orbit coupling and acoustic phonon scattering in weakly confined quantum dots with up to five interacting electrons. The full configuration interaction approach is used to account for the interelectron repulsion, and Rashba and Dresselhaus spin-orbit couplings are exactly diagonalized. We show that electron-electron interaction strongly affects spin-orbit admixture in the sample. Consequently, relaxation rates strongly depend on the number of carriers confined in the dot. We identify the mechanisms which may lead to improved spin stability in few electron (> 2) quantum dots as compared to the usual one and two electron devices. Finally, we discuss recent experiments on triplet-singlet transitions in GaAs dots subject to external magnetic fields. Our simulations are in good agreement with the experimental findings, and support the interpretation of the observed spin relaxation as being due to spin-orbit coupling assisted by acoustic phonon emission.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/11380/5978622007-01-01T00:00:00ZCarbon nanotubes as excitonic insulatorshttp://hdl.handle.net/11380/1155113Titolo: Carbon nanotubes as excitonic insulators
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/11380/11551132017-01-01T00:00:00Z