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Domain Textures in the Fractional Quantum Hall Effect
Ziyu Liu, Ursula Wurstbauer, Lingjie Du +4
Impacts of domain textures on low-lying neutral excitations in the bulk of fractional quantum Hall effect (FQHE) systems are probed by resonant inelastic light scattering. We demon…
Observation of flat bands in gated semiconductor artificial graphene
Lingjie Du, Ziyu Liu, Shalom J. Wind +6
Flat bands near M points in the Brillouin zone are key features of honeycomb symmetry in artificial graphene (AG) where electrons may condense into novel correlated phases. Here we…
Observation of new plasmons in the fractional quantum Hall effect: interplay of topological and nematic orders
Lingjie Du, Ursula Wurstbauer, Ken W. West +5
Collective modes of exotic quantum fluids reveal underlying physical mechanisms responsible for emergent complex quantum ground states. We observe unexpected new collective modes i…
Optical emission spectroscopy study of competing phases of electrons in the second Landau level
A. L. Levy, U. Wurstbauer, Y. Y. Kuznetsova +6
Quantum phases of electrons in the filling factor range are probed by the weak optical emission from the partially populated second Landau level and spin wave measu…
Fabrication of Artificial Graphene in a GaAs Quantum Heterostructure
Diego Scarabelli, Sheng Wang, Yuliya Y. Kuznetsova +7
The unusual electronic properties of graphene, which are a direct consequence of its two-dimensional (2D) honeycomb lattice, have attracted a great deal of attention in recent year…
Gapped Excitations of unconventional FQHE states in the Second Landau Level
U. Wurstbauer, A. L. Levy, A. Pinczuk +5
We report the observation of low-lying collective charge and spin excitations in the second Landau level at ν = 2 + 1/3 and also for the very fragile states at ν = 2 + 2/5, 2 + 3/8…
Evidence of inter-layer interaction in magneto-luminescence spectra of electron bilayers
Ilirjan Aliaj, Vittorio Pellegrini, Andrea Gamucci +4
Magneto-luminescence studies in electron bilayers reveal the hallmarks of the even-denominator and other quantum Hall states in the intensities and energies of the inter-band optic…
Experimental evidence of low-lying gapped excitations in the quantum fluid at nu=5/2
U. Wurstbauer, K. W. West, L. N. Pfeiffer +1
The low-lying neutral excitation spectrum of the incompressible quantum Hall fluid at is investigated by inelastic light scattering. Gapped modes are observable only in a v…
Probing the spin states of three interacting electrons in quantum dots
Andrea Gamucci, Vittorio Pellegrini, Achintya Singha +4
We observe a low-lying sharp spin mode of three interacting electrons in an array of nanofabricated AlGaAs/GaAs quantum dots by means of resonant inelastic light scattering. The fi…
Correlated electrons in optically-tunable quantum dots: Building an electron dimer molecule
Achintya Singha, Vittorio Pellegrini, Aron Pinczuk +3
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…
Engineering artificial graphene in a two-dimensional electron gas
M. Gibertini, A. Singha, V. Pellegrini +5
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…
A molecular state of correlated electrons in a quantum dot
Sokratis Kalliakos, Massimo Rontani, Vittorio Pellegrini +6
Correlation among particles in finite quantum systems leads to complex behaviour and novel states of matter. One remarkable example is predicted to occur in a semiconductor quantum…
Optical Anisotropy of Electronic Excitations in Elliptical Quantum Dots
Achintya Singha, Vittorio Pellegrini, Sokratis Kalliakos +4
The authors report that anisotropic confining potentials in laterally-coupled semiconductor quantum dots (QDs) have large impacts in optical transitions and energies of inter-shell…
Evidence of a first-order quantum phase transition of excitons in electron double layers
Biswajit Karmakar, Vittorio Pellegrini, Aron Pinczuk +2
Complexity in many-particle systems occurs through processes of qualitative differentiation. These are described by concepts such as emerging states with specific symmetries that a…
Optical control of energy-level structure of few electrons in AlGaAs/GaAs quantum dots
Sokratis Kalliakos, Vittorio Pellegrini, Cesar Pascual Garcia +3
Optical control of the lateral quantum confinement and number of electrons confined in nanofabricated GaAs/AlGaAs quantum dots is achieved by illumination with a weak laser beam th…
Observation of Anomalous Phonon Softening in Bilayer Graphene
Jun Yan, Erik A. Henriksen, Philip Kim +1
The interaction of electron-hole pairs with lattice vibrations exhibits a wealth of intriguing physical phenomena. The Kohn anomaly is a renowned example where electron-phonon coup…
Soft Spin Wave Near nu=1: Evidence for a Magnetic Instability in Skyrmion Systems
Y. Gallais, J. Yan, A. Pinczuk +2
The ground state of the two dimensional electron gas near =1 is investigated by inelastic light scattering measurements carried down to very low temperatures. Away from =1, t…
Metamorphosis of a Quantum Hall Bilayer State into a Composite Fermion Metal
Biswajit Karmakar, Stefano Luin, Vittorio Pellegrini +4
Composite fermion metal states emerge in quantum Hall bilayers at total Landau level filling factor =1 when the tunneling gap collapses by application of in-plane components o…
The Fermi edge singularity of spin polarized electrons
P. Plochocka-Polack, J. G. Groshaus, M. Rappaport +4
We study the absorption spectrum of a two-dimensional electron gas (2DEG) in a magnetic field. We find that that at low temperatures, when the 2DEG is spin polarized, the absorptio…
Electric Field Effect Tuning of Electron-Phonon Coupling in Graphene
Jun Yan, Yuanbo Zhang, Philip Kim +1
Gate-modulated low-temperature Raman spectra reveal that the electric field effect (EFE), pervasive in contemporary electronics, has marked impacts on long wavelength optical phono…
Absorption in the fractional quantum Hall regime: trion dichroism and spin polarization
J. G. Groshaus, P. Plochocka-Polack, M. Rappaport +7
We present measurements of optical interband absorption in the fractional quantum Hall regime in a GaAs quantum well in the range 0 < nu < 1. We investigate the mechanism of single…
Transition from Free to Interacting Composite Fermions away from =1/3
Y. Gallais, T. H. Kirschenmann, I. Dujovne +5
Spin excitations from a partially populated composite fermion level are studied above and below . In the range the experiments uncover significant departures fro…
Resonant Rayleigh scattering from quantum phases of cold electrons in semiconductor heterostructures
S. Luin, V. Pellegrini, A. Pinczuk +3
Resonant Rayleigh scattering of light from electrons confined in gallium arsenide double quantum wells displays significant changes at temperatures that are below one degree Kelvin…
Spin excitations in the Fractional Quantum Hall regime at
Y. Gallais, T. H. Kirschenmann, C. F. Hirjibehedin +4
We report inelastic light scattering experiments in the fractional quantum Hall regime at filling factors . A spin mode is observed below the Zeeman energy. The filli…