G. Goldoni - Academia.edu (original) (raw)
Papers by G. Goldoni
Physical Review B, 1995
We calculate the hole band structure and effective masses in a two-dimensional hole gas (2DHG) in... more We calculate the hole band structure and effective masses in a two-dimensional hole gas (2DHG) in p-doped [113]-grown heterojunctions. A Hamiltonian for the 2DHG is derived which is formally similar to the Luttinger Hamiltonian which describes the hole gas in conventional [001] heterojunctions. We use a limited analytical basis set of uncoupled heavy-hole and light-hole states which allow us to
Physical Review B, 2000
We investigate theoretically the spatial dependence of the linear absorption spectra of single an... more We investigate theoretically the spatial dependence of the linear absorption spectra of single and coupled semiconductor quantum dots, where the strong three-dimensional quantum confinement leads to an overall enhancement of Coulomb interaction and, in turn, to a pronounced renormalization of the excitonic properties. We show that-because of such Coulomb correlations and the spatial interference of the exciton wave functions-unexpected spectral features appear whose intensity depends on spatial resolution in a highly nonmonotonic way when the spatial resolution is comparable with the excitonic Bohr radius. We finally discuss how the optical near-field properties of double quantum dots are affected by their coupling.
Nonlinear Optics and Applications III, 2009
Large built-in piezoelectric fields in nitride nanostructures, because of their wurtzite structur... more Large built-in piezoelectric fields in nitride nanostructures, because of their wurtzite structure, induce a spatial seperation between confined electrons and holes and lead to formation of electric dipoles. This paper investigates the effects of exciton-exciton interaction as a dipolar interaction in a GaN/Al x Ga 1−x N microdisk. We show how this interaction result in biexciton binding energies in the meV energy range. Also we study the effect of disk radius on exciton binding energy. Results show that the exciton binding energy in smaller disks, is larger than the bigger one.
Physical review. B, Condensed matter, Jan 15, 1995
We study the electronic structure of a (100/103)-Å GaAs/Al0.35Ga0.65As multiple quantum-well samp... more We study the electronic structure of a (100/103)-Å GaAs/Al0.35Ga0.65As multiple quantum-well sample using the resonant enhancement of disorder-induced continuous Raman emission by acoustic phonons at interband magneto-optical transitions between Landau levels. Calculations are compared to fan plots of excitation energy vs resonance magnetic field and material parameters are determined. We find a significant difference between the electron effective mass for
Physical review. B, Condensed matter, Jan 15, 1996
We investigate the stability, the dynamical properties and melting of a two-dimensional (2D) Wign... more We investigate the stability, the dynamical properties and melting of a two-dimensional (2D) Wigner crystal (WC) of classical Coulombic particles in a bi-layer structure. Compared to the single-layer WC, this system shows a rich phase diagram. Five different crystalline phases are stable; the energetically favoured structure can be tuned by changing either the inter-layer distance or the particle density. Phase boundaries consist of both continuous and discontinuous transitions. We calculated the phonon excitations of the system within the harmonic approximation and we evaluated the melting temperature of the bi-layer WC by use of a modified Lindemann criterion, appropriate to 2D systems. We minimized the harmonic free-energy of the system with respect to the lattice geometry at different values of temperature/inter-layer distance and we found no temperature-induced structural phase transition.
New Directions in Mesoscopic Physics (Towards Nanoscience), 2003
Coupled semiconductor quantum dots form artificial molecules where relevant energy scales control... more Coupled semiconductor quantum dots form artificial molecules where relevant energy scales controlling the interacting ground state can be easily tuned. By applying an external magnetic field it is possible to drive the system from a weak to a strong correlation regime where eventually electrons localize in space in an ordered manner reminiscent of the two-dimensional Wigner crystal. We explore the phase diagram of such "Wigner molecules" analyzing the angular correlation function obtained by the Configuration Interaction solution of the full interacting Hamiltonian. Focus is on the role of tunneling in stabilizing different ground states.
NATO Science Series, 2005
We discuss the properties of few electrons and electron-hole pairs confined in coupled semiconduc... more We discuss the properties of few electrons and electron-hole pairs confined in coupled semiconductor quantum dots, with emphasis on correlation effects and the role of tunneling. We shall discuss, in particular, exact diagonalization results for biexciton binding energy, electron-hole localization, magnetic-field induced Wigner molecules, and spin ordering.
Semiconductor Science and Technology, 2002
We compute the exact lowest energy states and addition spectra for N interacting carriers in semi... more We compute the exact lowest energy states and addition spectra for N interacting carriers in semiconductor quantum dots (QDs) embedded in low-dielectric-constant matrices. In particular we focus on the transition between the low dielectric mismatch regime, where single-particle states are confined inside the QD, and the large mismatch regime, where surface localized states may be induced by the dielectric potential
Physica E: Low-Dimensional Systems and Nanostructures, 2008
We compute carrier states on a cylindrical 2DEG under the influence of a magnetic field perpendic... more We compute carrier states on a cylindrical 2DEG under the influence of a magnetic field perpendicular to the tube axis. The field and the topology of the cylindrical surface have been included in the Schrödinger equation, that has been solved exactly. The results ...
Physical Review B, 2007
We study the effect of Coulomb interaction on the few-electron dynamics in coupled semiconductor ... more We study the effect of Coulomb interaction on the few-electron dynamics in coupled semiconductor quantum dots by exact diagonalization of the few-body Hamiltonian. The oscillation of carriers is strongly affected by the number of confined electrons and by the strength of the interdot correlations. Single-frequency oscillations are found for either uncorrelated or highly correlated states, while multi-frequency oscillations take place in the intermediate regime. Moreover, Coulomb interaction renders few-particle oscillations sensitive to perturbations in spatial directions other than that of the tunneling, contrary to the single-particle case. The inclusion of acoustic phonon scattering does not modify the carrier dynamics substantially at short times, but can damp oscillation modes selectively at long times. PACS numbers: 73.21.La, 03.67.Lx, 72.10.Di Low-dimensional heterostructures enable direct probing of the time evolution of carriers. In particular, charge oscillations between coupled quantum structures have been measured in a number of different systems, such as Josephson junctions [1], quantum wells [2], or quantum dots . Coupled quantum dots (CQDs), where the number of confined carriers can be controlled experimentally, are a most interesting case as they posses a discrete energy spectrum which stems from the quantum confinement in all three spatial directions, thus constituting the physical realization of the particle-in-the-box problem. Understanding charge oscillations in these structures is not only of fundamental importance but also of technological relevance, since control of the coherent dynamics of charge states is at the base of many proposals for novel nanoelectronic devices and quantum logic gates . This has motivated recent attempts to achieve control of charge localization and dynamics in CQD systems by means of microwave excitations , static[4] and time-dependent[12, 13] electric fields.
Journal of Computational Electronics, 2006
We present a method for the calculation of the scattering states of a N + 1th-particle coherently... more We present a method for the calculation of the scattering states of a N + 1th-particle coherently interacting with N correlated particles confined in a nanostructure and placed within an open domain. The method is based on a generalization of the quantum transmitting boundary method [C. Lent and D. Kirkner, J. App. Phys. 67, 6353 (1990)]. The antisymmetry conditions of the N + 1-identical particles current-carrying state results from a proper choice of the boundary conditions. As an example which is relevant to coherent electronics, we apply the method to compute the exact transmission functions and phases of an electron crossing a 1D quantum dot with zero, one or two bound electrons.
Theoretical Chemistry Accounts, 2012
ABSTRACT We report on ab-initio calculations of the electronic structure and optical absorption r... more ABSTRACT We report on ab-initio calculations of the electronic structure and optical absorption response of the black dye sensitizer in gas phase. We show that, despite the large size of this molecule, the second-order multiconfiguration quasi-degenerate perturbation theory (MC-QDPT) can be used to calculate vertical excitation energies, oscillator strengths and optical absorption spectra. The zeroth-order reference states entering perturbation calculations are complete active space (CAS) configuration interaction (CI) wave functions computed for 12 active electrons distributed in 12 active orbitals. We found that the CI approach is not enough for taking into account the strong dynamical correlation effects in this system. In fact, the excitation energies of the CAS-CI target states are strongly renormalized by the MC-QDPT calculations. In the calculated absorption spectra, the analysis of the perturbed wavefunctions revealed that the stronger absorption bands correspond to metal-to-ligand and ligand-to-ligand charge transfer processes. Comparison with independent time-dependent extension (TDDFT) calculations performed with different functionals shows that corrections to the long-range behavior of the functional is pivotal to achieve agreement with the MC-QDPT results.
Surface Science, 1996
We investigate the zero-temperature phase diagram and melting transition of a two-dimensional Wig... more We investigate the zero-temperature phase diagram and melting transition of a two-dimensional Wigner crystal (WC) of classical Coulombic particles in a double-layer structure. In oontrast with the single-layer WC, we find that five different crystalline phases are stable in different ranges of inter-layer distance/particle density. Phase boundaries consist of both continuous and discontinuous transitions. From the phonon frequencies of the system we evaluate the melting temperature of the WC. We suggest the possibility of structural phase transitions as a function of temperature.
Surface Science, 1989
The initial steps in the use of surface sensitive experimental probes to study high-temperature s... more The initial steps in the use of surface sensitive experimental probes to study high-temperature superconductors were negatively affected by doubts about surface quality. A significant improvement was the success in cleaving different kinds of high-T c single crystals under ultrahigh vacuum conditions. We present results obtained on cleaved 1-2-3 and Bi4Ca3SrgCu4Ol6 ~ • surfaces with electron diffusion and synchrotron radiation photoemission spectroscopy.
Physical Review Letters, 2007
We have applied the quantum Monte Carlo method and tight-binding modelling to calculate the bindi... more We have applied the quantum Monte Carlo method and tight-binding modelling to calculate the binding energy of biexcitons in semiconductor carbon nanotubes for a wide range of diameters and chiralities. For typical nanotube diameters we find that biexciton binding energies are much larger than previously predicted from variational methods, which easily brings the biexciton binding energy above the room temperature threshold. PACS numbers: 73.22.Lp, 73.20.Mf, Size-dependent optical excitations in nano-structures are at the heart of fundamental studies as well as conceivable applications . Carbon nanotubes (CNTs) make no exception, showing very sensitive electronic and optical properties to the atomic structure and spanning a wide range of wavelengths . The stability of the excitonic states, neutral or charged optically excited electron-hole complexes, is determined by their binding energy with respect to thermal fluctuations. In quasi-1D systems, the binding energy can be much larger than in systems of higher dimensionality. In inorganic semiconductor heterostructures, for instance, the exciton binding energy E X b is substantially larger than [3, 4, 5] the binding energy 4 Ry * in a strictly 2D system , where Ry * is the Rydberg energy of the host material. Analogously, the biexciton binding energy E XX b of two electron-hole pairs, optically excited in a two-photon process, is not limited to its 2D value of 0.77 Ry * [9, 10].
Physical Review Letters, 2005
We theoretically analyze the optical near-field response of a semiconductor macroatom induced by ... more We theoretically analyze the optical near-field response of a semiconductor macroatom induced by local monolayer fluctuations in the thickness of a semiconductor quantum well, where the large active volume results in a strong enhancement of the light-matter coupling. We find that in the near-field regime bright and dark excitonic states become mixed, opening new channels for the coupling to the electromagnetic field. As a consequence, ultranarrow luminescence lines appear in the simulated two-photon experiments, corresponding to very long lived excitonic states, which undergo Stark shift and Rabi splitting at relatively small field intensities.
Physical Review Letters, 1997
The scaling of exciton binding energy in semiconductor quantum wires is investigated theoreticall... more The scaling of exciton binding energy in semiconductor quantum wires is investigated theoretically through a non-variational, fully three-dimensional approach for a wide set of realistic state-of-the-art structures. We find that in the strong confinement limit the same potential-to-kinetic energy ratio holds for quite different wire cross-sections and compositions. As a consequence, a universal (shape-and composition-independent) parameter can be identified that governs the scaling of the binding energy with size. Previous indications that the shape of the wire cross-section may have important effects on exciton binding are discussed in the light of the present results. 78.66.Fd, 73.20.Dx Typeset using REVT E X
Physical Review Letters, 2005
We report inelastic light scattering measurements of spin and charge excitations in nanofabricate... more We report inelastic light scattering measurements of spin and charge excitations in nanofabricated AlGaAs/GaAs quantum dots with few electrons. A narrow spin excitation peak is observed and assigned to the intershell triplet-to-singlet monopole mode of dots with four electrons. Configurationinteraction theory provides precise quantitative interpretations that uncover large correlation effects that are comparable to exchange Coulomb interactions.
Physical Review B, 2008
We present a full configuration interaction study of the spontaneous recombination of neutral and... more We present a full configuration interaction study of the spontaneous recombination of neutral and singly charged excitons (trions) in semiconductor quantum dots, from weak to strong coupling regimes. We find that the enhancement of the recombination rate of neutral excitons with increasing dot size is suppressed for negative trions, and even reversed for positive trions. Our findings agree with recent comprehensive photoluminescence experiments in self-assembled quantum dots [P. Dalgarno et al. Phys. Rev. B 77, 245311 (2008)] and confirm the major role played by correlations in the valence band. The effect of the temperature on the photoluminescence spectrum and that of the ratio between the electron and hole wavefunction lengthscales are also described.
Physical Review B, 1995
We calculate the hole band structure and effective masses in a two-dimensional hole gas (2DHG) in... more We calculate the hole band structure and effective masses in a two-dimensional hole gas (2DHG) in p-doped [113]-grown heterojunctions. A Hamiltonian for the 2DHG is derived which is formally similar to the Luttinger Hamiltonian which describes the hole gas in conventional [001] heterojunctions. We use a limited analytical basis set of uncoupled heavy-hole and light-hole states which allow us to
Physical Review B, 2000
We investigate theoretically the spatial dependence of the linear absorption spectra of single an... more We investigate theoretically the spatial dependence of the linear absorption spectra of single and coupled semiconductor quantum dots, where the strong three-dimensional quantum confinement leads to an overall enhancement of Coulomb interaction and, in turn, to a pronounced renormalization of the excitonic properties. We show that-because of such Coulomb correlations and the spatial interference of the exciton wave functions-unexpected spectral features appear whose intensity depends on spatial resolution in a highly nonmonotonic way when the spatial resolution is comparable with the excitonic Bohr radius. We finally discuss how the optical near-field properties of double quantum dots are affected by their coupling.
Nonlinear Optics and Applications III, 2009
Large built-in piezoelectric fields in nitride nanostructures, because of their wurtzite structur... more Large built-in piezoelectric fields in nitride nanostructures, because of their wurtzite structure, induce a spatial seperation between confined electrons and holes and lead to formation of electric dipoles. This paper investigates the effects of exciton-exciton interaction as a dipolar interaction in a GaN/Al x Ga 1−x N microdisk. We show how this interaction result in biexciton binding energies in the meV energy range. Also we study the effect of disk radius on exciton binding energy. Results show that the exciton binding energy in smaller disks, is larger than the bigger one.
Physical review. B, Condensed matter, Jan 15, 1995
We study the electronic structure of a (100/103)-Å GaAs/Al0.35Ga0.65As multiple quantum-well samp... more We study the electronic structure of a (100/103)-Å GaAs/Al0.35Ga0.65As multiple quantum-well sample using the resonant enhancement of disorder-induced continuous Raman emission by acoustic phonons at interband magneto-optical transitions between Landau levels. Calculations are compared to fan plots of excitation energy vs resonance magnetic field and material parameters are determined. We find a significant difference between the electron effective mass for
Physical review. B, Condensed matter, Jan 15, 1996
We investigate the stability, the dynamical properties and melting of a two-dimensional (2D) Wign... more We investigate the stability, the dynamical properties and melting of a two-dimensional (2D) Wigner crystal (WC) of classical Coulombic particles in a bi-layer structure. Compared to the single-layer WC, this system shows a rich phase diagram. Five different crystalline phases are stable; the energetically favoured structure can be tuned by changing either the inter-layer distance or the particle density. Phase boundaries consist of both continuous and discontinuous transitions. We calculated the phonon excitations of the system within the harmonic approximation and we evaluated the melting temperature of the bi-layer WC by use of a modified Lindemann criterion, appropriate to 2D systems. We minimized the harmonic free-energy of the system with respect to the lattice geometry at different values of temperature/inter-layer distance and we found no temperature-induced structural phase transition.
New Directions in Mesoscopic Physics (Towards Nanoscience), 2003
Coupled semiconductor quantum dots form artificial molecules where relevant energy scales control... more Coupled semiconductor quantum dots form artificial molecules where relevant energy scales controlling the interacting ground state can be easily tuned. By applying an external magnetic field it is possible to drive the system from a weak to a strong correlation regime where eventually electrons localize in space in an ordered manner reminiscent of the two-dimensional Wigner crystal. We explore the phase diagram of such "Wigner molecules" analyzing the angular correlation function obtained by the Configuration Interaction solution of the full interacting Hamiltonian. Focus is on the role of tunneling in stabilizing different ground states.
NATO Science Series, 2005
We discuss the properties of few electrons and electron-hole pairs confined in coupled semiconduc... more We discuss the properties of few electrons and electron-hole pairs confined in coupled semiconductor quantum dots, with emphasis on correlation effects and the role of tunneling. We shall discuss, in particular, exact diagonalization results for biexciton binding energy, electron-hole localization, magnetic-field induced Wigner molecules, and spin ordering.
Semiconductor Science and Technology, 2002
We compute the exact lowest energy states and addition spectra for N interacting carriers in semi... more We compute the exact lowest energy states and addition spectra for N interacting carriers in semiconductor quantum dots (QDs) embedded in low-dielectric-constant matrices. In particular we focus on the transition between the low dielectric mismatch regime, where single-particle states are confined inside the QD, and the large mismatch regime, where surface localized states may be induced by the dielectric potential
Physica E: Low-Dimensional Systems and Nanostructures, 2008
We compute carrier states on a cylindrical 2DEG under the influence of a magnetic field perpendic... more We compute carrier states on a cylindrical 2DEG under the influence of a magnetic field perpendicular to the tube axis. The field and the topology of the cylindrical surface have been included in the Schrödinger equation, that has been solved exactly. The results ...
Physical Review B, 2007
We study the effect of Coulomb interaction on the few-electron dynamics in coupled semiconductor ... more We study the effect of Coulomb interaction on the few-electron dynamics in coupled semiconductor quantum dots by exact diagonalization of the few-body Hamiltonian. The oscillation of carriers is strongly affected by the number of confined electrons and by the strength of the interdot correlations. Single-frequency oscillations are found for either uncorrelated or highly correlated states, while multi-frequency oscillations take place in the intermediate regime. Moreover, Coulomb interaction renders few-particle oscillations sensitive to perturbations in spatial directions other than that of the tunneling, contrary to the single-particle case. The inclusion of acoustic phonon scattering does not modify the carrier dynamics substantially at short times, but can damp oscillation modes selectively at long times. PACS numbers: 73.21.La, 03.67.Lx, 72.10.Di Low-dimensional heterostructures enable direct probing of the time evolution of carriers. In particular, charge oscillations between coupled quantum structures have been measured in a number of different systems, such as Josephson junctions [1], quantum wells [2], or quantum dots . Coupled quantum dots (CQDs), where the number of confined carriers can be controlled experimentally, are a most interesting case as they posses a discrete energy spectrum which stems from the quantum confinement in all three spatial directions, thus constituting the physical realization of the particle-in-the-box problem. Understanding charge oscillations in these structures is not only of fundamental importance but also of technological relevance, since control of the coherent dynamics of charge states is at the base of many proposals for novel nanoelectronic devices and quantum logic gates . This has motivated recent attempts to achieve control of charge localization and dynamics in CQD systems by means of microwave excitations , static[4] and time-dependent[12, 13] electric fields.
Journal of Computational Electronics, 2006
We present a method for the calculation of the scattering states of a N + 1th-particle coherently... more We present a method for the calculation of the scattering states of a N + 1th-particle coherently interacting with N correlated particles confined in a nanostructure and placed within an open domain. The method is based on a generalization of the quantum transmitting boundary method [C. Lent and D. Kirkner, J. App. Phys. 67, 6353 (1990)]. The antisymmetry conditions of the N + 1-identical particles current-carrying state results from a proper choice of the boundary conditions. As an example which is relevant to coherent electronics, we apply the method to compute the exact transmission functions and phases of an electron crossing a 1D quantum dot with zero, one or two bound electrons.
Theoretical Chemistry Accounts, 2012
ABSTRACT We report on ab-initio calculations of the electronic structure and optical absorption r... more ABSTRACT We report on ab-initio calculations of the electronic structure and optical absorption response of the black dye sensitizer in gas phase. We show that, despite the large size of this molecule, the second-order multiconfiguration quasi-degenerate perturbation theory (MC-QDPT) can be used to calculate vertical excitation energies, oscillator strengths and optical absorption spectra. The zeroth-order reference states entering perturbation calculations are complete active space (CAS) configuration interaction (CI) wave functions computed for 12 active electrons distributed in 12 active orbitals. We found that the CI approach is not enough for taking into account the strong dynamical correlation effects in this system. In fact, the excitation energies of the CAS-CI target states are strongly renormalized by the MC-QDPT calculations. In the calculated absorption spectra, the analysis of the perturbed wavefunctions revealed that the stronger absorption bands correspond to metal-to-ligand and ligand-to-ligand charge transfer processes. Comparison with independent time-dependent extension (TDDFT) calculations performed with different functionals shows that corrections to the long-range behavior of the functional is pivotal to achieve agreement with the MC-QDPT results.
Surface Science, 1996
We investigate the zero-temperature phase diagram and melting transition of a two-dimensional Wig... more We investigate the zero-temperature phase diagram and melting transition of a two-dimensional Wigner crystal (WC) of classical Coulombic particles in a double-layer structure. In oontrast with the single-layer WC, we find that five different crystalline phases are stable in different ranges of inter-layer distance/particle density. Phase boundaries consist of both continuous and discontinuous transitions. From the phonon frequencies of the system we evaluate the melting temperature of the WC. We suggest the possibility of structural phase transitions as a function of temperature.
Surface Science, 1989
The initial steps in the use of surface sensitive experimental probes to study high-temperature s... more The initial steps in the use of surface sensitive experimental probes to study high-temperature superconductors were negatively affected by doubts about surface quality. A significant improvement was the success in cleaving different kinds of high-T c single crystals under ultrahigh vacuum conditions. We present results obtained on cleaved 1-2-3 and Bi4Ca3SrgCu4Ol6 ~ • surfaces with electron diffusion and synchrotron radiation photoemission spectroscopy.
Physical Review Letters, 2007
We have applied the quantum Monte Carlo method and tight-binding modelling to calculate the bindi... more We have applied the quantum Monte Carlo method and tight-binding modelling to calculate the binding energy of biexcitons in semiconductor carbon nanotubes for a wide range of diameters and chiralities. For typical nanotube diameters we find that biexciton binding energies are much larger than previously predicted from variational methods, which easily brings the biexciton binding energy above the room temperature threshold. PACS numbers: 73.22.Lp, 73.20.Mf, Size-dependent optical excitations in nano-structures are at the heart of fundamental studies as well as conceivable applications . Carbon nanotubes (CNTs) make no exception, showing very sensitive electronic and optical properties to the atomic structure and spanning a wide range of wavelengths . The stability of the excitonic states, neutral or charged optically excited electron-hole complexes, is determined by their binding energy with respect to thermal fluctuations. In quasi-1D systems, the binding energy can be much larger than in systems of higher dimensionality. In inorganic semiconductor heterostructures, for instance, the exciton binding energy E X b is substantially larger than [3, 4, 5] the binding energy 4 Ry * in a strictly 2D system , where Ry * is the Rydberg energy of the host material. Analogously, the biexciton binding energy E XX b of two electron-hole pairs, optically excited in a two-photon process, is not limited to its 2D value of 0.77 Ry * [9, 10].
Physical Review Letters, 2005
We theoretically analyze the optical near-field response of a semiconductor macroatom induced by ... more We theoretically analyze the optical near-field response of a semiconductor macroatom induced by local monolayer fluctuations in the thickness of a semiconductor quantum well, where the large active volume results in a strong enhancement of the light-matter coupling. We find that in the near-field regime bright and dark excitonic states become mixed, opening new channels for the coupling to the electromagnetic field. As a consequence, ultranarrow luminescence lines appear in the simulated two-photon experiments, corresponding to very long lived excitonic states, which undergo Stark shift and Rabi splitting at relatively small field intensities.
Physical Review Letters, 1997
The scaling of exciton binding energy in semiconductor quantum wires is investigated theoreticall... more The scaling of exciton binding energy in semiconductor quantum wires is investigated theoretically through a non-variational, fully three-dimensional approach for a wide set of realistic state-of-the-art structures. We find that in the strong confinement limit the same potential-to-kinetic energy ratio holds for quite different wire cross-sections and compositions. As a consequence, a universal (shape-and composition-independent) parameter can be identified that governs the scaling of the binding energy with size. Previous indications that the shape of the wire cross-section may have important effects on exciton binding are discussed in the light of the present results. 78.66.Fd, 73.20.Dx Typeset using REVT E X
Physical Review Letters, 2005
We report inelastic light scattering measurements of spin and charge excitations in nanofabricate... more We report inelastic light scattering measurements of spin and charge excitations in nanofabricated AlGaAs/GaAs quantum dots with few electrons. A narrow spin excitation peak is observed and assigned to the intershell triplet-to-singlet monopole mode of dots with four electrons. Configurationinteraction theory provides precise quantitative interpretations that uncover large correlation effects that are comparable to exchange Coulomb interactions.
Physical Review B, 2008
We present a full configuration interaction study of the spontaneous recombination of neutral and... more We present a full configuration interaction study of the spontaneous recombination of neutral and singly charged excitons (trions) in semiconductor quantum dots, from weak to strong coupling regimes. We find that the enhancement of the recombination rate of neutral excitons with increasing dot size is suppressed for negative trions, and even reversed for positive trions. Our findings agree with recent comprehensive photoluminescence experiments in self-assembled quantum dots [P. Dalgarno et al. Phys. Rev. B 77, 245311 (2008)] and confirm the major role played by correlations in the valence band. The effect of the temperature on the photoluminescence spectrum and that of the ratio between the electron and hole wavefunction lengthscales are also described.