http://192.168.1.40:8080/xmlui/handle/123456789/1332 Sun, 31 May 2026 10:40:39 GMT 2026-05-31T10:40:39Z http://192.168.1.40:8080/xmlui/handle/123456789/1693 Optical anisotropy of electronic excitations in elliptical quantum dots Singha, Achintya; Pellegrini, Vittorio; Kalliakos, Sokratis; Karmakar, Biswajit; Pinczuk, Aron; Pfeiffer, Loren N.; West, Ken W. The authors report that anisotropic confining potentials in laterally coupled semiconductor quantum dots (QDs) have large impacts in optical transitions and energies of intershell collective electronic excitations. The observed anisotropies are revealed by inelastic light scattering as a function of the in-plane direction of light polarization and can be finely controlled by modifying the geometrical shape of the QDs. These experiments show that the tuning of the QD confinement potential offers a powerful method to manipulate electronic states and far-infrared intershell optical transitions in QDs. DOI: 10.1063/1.3080658 Mon, 16 Feb 2009 00:00:00 GMT http://192.168.1.40:8080/xmlui/handle/123456789/1693 2009-02-16T00:00:00Z http://192.168.1.40:8080/xmlui/handle/123456789/1691 Probing collective modes of correlated states of few electrons in semiconductor quantum dots Kalliakos, S.; Rontani, M.; Pellegrini, V.; Pinczuk, A.; Singha, Achintya; Garcia, C. P.; Goldoni, G.; Molinari, E.; Pfeiffer, L. N.; West, K. W. 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. DOI: 10.1016/j.ssc.2009.04.034 Tue, 01 Sep 2009 00:00:00 GMT http://192.168.1.40:8080/xmlui/handle/123456789/1691 2009-09-01T00:00:00Z http://192.168.1.40:8080/xmlui/handle/123456789/1690 Engineering artificial graphene in a two-dimensional electron gas Gibertini, M.; Singha, Achintya; Pellegrini, Vittorio; Polini, Marco; Vignale, Giovanni; Pinczuk, Aron; Pfeiffer, Loren N.; West, Ken W. At low energy, electrons in doped graphene sheets behave like massless Dirac fermions with a Fermi velocity, which does not depend on carrier density. Here we show that modulating a two-dimensional electron gas with a long-wavelength periodic potential with honeycomb symmetry can lead to the creation of isolated massless Dirac points with tunable Fermi velocity. We provide detailed theoretical estimates to realize such artificial graphenelike system and discuss an experimental realization in a modulation-doped GaAs quantum well. Ultrahigh-mobility electrons with linearly dispersing bands might open new venues for the studies of Dirac-fermion physics in semiconductors. DOI: 10.1103/PhysRevB.79.241406 Mon, 01 Jun 2009 00:00:00 GMT http://192.168.1.40:8080/xmlui/handle/123456789/1690 2009-06-01T00:00:00Z http://192.168.1.40:8080/xmlui/handle/123456789/1338 Correlated electrons in optically tunable quantum dots: Building an electron dimer molecule Singha, Achintya; Pellegrini, Vittorio; Pinczuk, Aron; Pfeiffer, Loren N.; West, Ken W.; Rontani, Massimo We observe the low-lying excitations of a molecular dimer formed by two electrons in a GaAs semiconductor quantum dot in which the number of confined electrons is tuned by optical illumination. By employing inelastic light scattering we identify the intershell excitations in the one-electron regime and the distinct spin and charge modes in the interacting few-body configuration. In the case of two electrons, a comparison with configuration-interaction calculations allows us to link the observed excitations with the breathing mode of the molecular dimer and to determine the singlet-triplet energy splitting. DOI: 10.1103/PhysRevLett.104.246802 Tue, 15 Jun 2010 00:00:00 GMT http://192.168.1.40:8080/xmlui/handle/123456789/1338 2010-06-15T00:00:00Z