Exciton binding energies and diamagnetic shifts in semiconductor quantum wires and quantum dots

Bayer, М.; Walck, Scott N.; Reinecke, T. L.; Forchel, A.

doi:10.1103/physrevb.57.6584

Cited by 120 publications

(65 citation statements)

References 23 publications

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“…This is justified in our experimental conditions (weak magnetic fields) due to much smaller cyclotron energy when compared to the exciton binding energy of the investigated structures [4,9,69,70]. In this case, the diamagnetic coefficient κ can be expressed as follows [71]:…”

Section: A Diamagnetic Coefficientmentioning

confidence: 73%

Toward weak confinement regime in epitaxial nanostructures: Interdependence of spatial character of quantum confinement and wave function extension in large and elongated quantum dots

et al. 2014

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In this paper we present a comprehensive and detailed analysis of carrier/exciton wave function extension in large low-strain In 0.3 Ga 0.7 As quantum dots (QDs). They exhibit rather shallow confinement potential with electron/hole localization energy below 30 meV and confinement strength substantially weakened in comparison to typical epitaxial quasi-zero-dimensional semiconductor nanostructures. The aim of this study is to investigate the influence of different factors on the wave function (probability density distribution) for carriers or excitons in this regime, i.e., object shape anisotropy as well as strain, piezoelectricity, and Coulomb interactions, and to identify the physical mechanisms determining the properties of optical emission. To probe the wave function symmetry, polarization-resolved photoluminescence has been performed, and the spatial extensions of the corresponding probability densities have been verified in magneto-optical measurements. The observed diamagnetic coefficients in the range of (15-31) μeV/T 2 reflect large in-plane QD size. These studies also enable us to investigate the importance of light hole states admixture to the valence band ground state in such nanostructures, which can be addressed via the degree of linear polarization of emission as well as the exciton g X factor. The linear-polarization-resolved measurements revealed an exceptionally low exciton fine structure splitting of 5 μeV on average as well as a low emission polarization degree of −0.05, with the polarization perpendicular to the QD elongation direction dominating. The increased light hole contribution to the lowest energy hole level is reflected in the decreased exciton g X factor (in the range of 0-1) and is consistent with the results of the eight-band k·p modelling. Based on the temperature dependence of the diamagnetic coefficient, the problem of individual QD uniformity has additionally been discussed. To evaluate the impact of the confinment potential and the structure geometry on the optical properties of the QDs, a comparison between the investigated dots and InAs/InGaAlAs/InP quantum dashes exhibiting a much deeper confining potential is presented.

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Section: A Diamagnetic Coefficientmentioning

confidence: 73%

Toward weak confinement regime in epitaxial nanostructures: Interdependence of spatial character of quantum confinement and wave function extension in large and elongated quantum dots

et al. 2014

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“…denotes the binding energy of the neutral exciton. Under an applied magnetic field, the exciton binding energies can acquire a diamagnetic shift, which is quadratic under in the B field [34,35]. Based on the observed linear variation of the transition energy with B, we infer, however, that this term is small.…”

mentioning

confidence: 76%

Valley Splitting and Polarization by Zeeman Effect in Monolayer MoSe2

Li¹,

Ludwig²,

Low³

et al. 2015

Probing the Response of Two-Dimensional Crystals by Optical Spectroscopy

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We have measured circularly polarized photoluminescence in monolayer MoSe 2 under perpendicular magnetic fields up to 10 T. At low doping densities, the neutral and charged excitons shift linearly with field strength at a rate of ∓ 0.12 meV/T for emission arising, respectively, from the K and K' valleys. The opposite sign for emission from different valleys demonstrates lifting of the valley degeneracy. The magnitude of the Zeeman shift agrees with predicted magnetic moments for carriers in the conduction and valence bands. The relative intensity of neutral and charged exciton emission is modified by the magnetic field, reflecting the creation of field-induced valley polarization. At high doping levels, the Zeeman shift of the charged exciton increases to ∓ 0.18 meV/T. This enhancement is attributed to many-body effects on the binding energy of the charged excitons.PACS numbers: 75.70. Ak, 78.20.Ls, 73.20.Mf, 73.22Monolayer MoSe 2 features two inequivalent valleys in the Brillouin zone of its electronic structure. The broken inversion symmetry of the monolayer allows this valley degree of freedom to be selectively accessed by optical helicity, providing a unique platform to probe and manipulate the charge carriers in the two valleys. [1][2][3][4][5][6][7][8] Since the valleys are linked by timereversal symmetry, they are energetically degenerate, while the magnetic moments of the corresponding valley states are of the same magnitude, but have opposite sign [1,9,10]. Coupling to the valley magnetic moments by a magnetic field thus provides an attractive, but as yet unexplored method of breaking the valley degeneracy [11,12]. This presents new opportunities for the study of the fundamental physical properties of the valley electronic states, as well as for the development of new approaches to valleytronic control.In this work, we experimentally investigate the ability of a perpendicular magnetic field to tune the valley energies in monolayer MoSe 2 by valley-resolved magneto-photoluminescence (magneto-PL) spectroscopy. Lifting of the valley degeneracy is demonstrated through the opposite energy shifts induced in the excitonic transitions in the two valleys by the magnetic field. The magnitude of this Zeeman shift, 0.12 meV/T, agrees with the predicted magnetic moments of the valley states. In the presence of a magnetic field, with split K and K' valleys, we create an equilibrium valley polarization, i.e., an imbalance in the charge distribution in the two valleys, by doping the sample. This behavior is revealed by the variation of the relative emission intensity of the charged and neutral excitons. Further, by comparing the direction of the energy shift of the conduction band and the relative intensity of the negatively charged exciton, we are able to clarify the valley configuration of these bright trion states. In addition, the doping dependent trion Zeeman shift reveals the modification to the many-body binding energy by the creation of valley polarization. 3MoSe 2 monolayers were prepared by mechanic...

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“…For QDs the binding energy ∆ b commonly exceeds the fine structure δ 0 by more than one order of magnitude ∆ b >> δ 0 [50,52]. Thus, the binding energy ∆ b also induces a comparably larger split between the dressed eigenenergies E ϕ 2/4 and E ϕ 1/3 compared to the fine structure inducing a split between the dressed states energies E ϕ 4 and E ϕ 2 .…”

Section: Photonic Coherences Under Resonant Two Photon Excitationmentioning

confidence: 99%

Optical control of nonlinearly dressed states in an individual quantum dot

et al. 2016

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We report two-photon resonance fluorescence of an individual semiconductor artificial atom. By non-linearly driving a single semiconductor quantum dot via a two-photon transition, we probe the linewidth of the two-photon processes and show that, similar to their single-photon counterparts, they are close to being Fourier limited at low temperatures. The evolution of the population of excitonic states with the Rabi frequency exhibits a clear s-shaped behavior, indicative of the nonlinear response via the two photon excitation process. We model the non-linear response using a 4-level atomic system representing the manifold of excitonic and biexcitonic states in the quantum dot and show that quantitative agreement is obtained only by including the interaction with LAphonons in the solid state environment. Finally, we demonstrate the formation of dressed states emerging from a two-photon interaction between the artificial atom and the excitation field. The non-linear optical dressing induces a mixing of all four excitonic states that facilitates the tuning of the polarization selection rules of the artificial atom.

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Exciton binding energies and diamagnetic shifts in semiconductor quantum wires and quantum dots

Cited by 120 publications

References 23 publications

Toward weak confinement regime in epitaxial nanostructures: Interdependence of spatial character of quantum confinement and wave function extension in large and elongated quantum dots

Toward weak confinement regime in epitaxial nanostructures: Interdependence of spatial character of quantum confinement and wave function extension in large and elongated quantum dots

Valley Splitting and Polarization by Zeeman Effect in Monolayer MoSe2

Optical control of nonlinearly dressed states in an individual quantum dot

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