Resonant Raman Transitions into Singlet and Triplet States in InGaAs Quantum Dots Containing Two Electrons

Köppen, T.; Franz, Dennis; Schramm, Andreas; Heyn, Ch.; Heitmann, D.; Kipp, Tobias

doi:10.1103/physrevlett.103.037402

Cited by 17 publications

(17 citation statements)

References 23 publications

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“…The energy difference of about 10 meV is a direct measure of the exchange interaction in self-assembled QDs, which has so far only been studied in self-assembled dots using optical spectroscopy95. The splitting is large enough to allow for the all-electrical preparation of spin-polarized states.…”

Section: Discussionmentioning

confidence: 99%

“…These visionary applications require a controlled preparation of non-equilibrium states with well-defined charge and spin degrees of freedom. For self-assembled QDs, great progress has been made in this field using optical excitation and detection methods567891011. Optical techniques, however, may be difficult to implement in highly integrated (classical or quantum) computer technologies.…”

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confidence: 99%

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Transport spectroscopy of non-equilibrium many-particle spin states in self-assembled quantum dots

et al. 2011

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Self-assembled quantum dots (QDs) are prominent candidates for solid-state quantum information processing. For these systems, great progress has been made in addressing spin states by optical means. In this study, we introduce an all-electrical measurement technique to prepare and detect non-equilibrium many-particle spin states in an ensemble of self-assembled QDs at liquid helium temperature. The excitation spectra of the one- (QD hydrogen), two- (QD helium) and three- (QD lithium) electron configuration are shown and compared with calculations using the exact diagonalization method. An exchange splitting of 10 meV between the excited triplet and singlet spin states is observed in the QD helium spectrum. These experiments are a starting point for an all-electrical control of electron spin states in self-assembled QDs above liquid helium temperature.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Transport spectroscopy of non-equilibrium many-particle spin states in self-assembled quantum dots

et al. 2011

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“…We also discuss, in extension to Ref. 19, QDs containing N = 1 electron. We observe resonantly excited PL emission between the ground state of electrons and holes and resonant Raman transitions from the electron ground state into the first excited electron state.…”

Section: Introductionmentioning

confidence: 89%

“…16 In this paper, we report on a more detailed and extended study of the results which are presented in a recent publication about resonant spectroscopy on InGaAs QDs containing N = 1,2 electrons. 19 For N = 2, these so-called QD-helium atoms are model structures to investigate the most fundamental manyparticle states, the singlet and triplet states which resemble the para-and the ortho-He states of the real He atoms. A key ingredient of our experiments is that we have prepared, utilizing the rapid thermal annealing technique, 20 quantum dots with fundamental excitation gaps of about 1.30 eV.…”

Section: Introductionmentioning

confidence: 99%

Elementary excitations in charge-tunable InGaAs quantum dots studied by resonant Raman and resonant photoluminescence spectroscopy

et al. 2011

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We report on resonant optical spectroscopy of self-assembled InGaAs quantum dots in which the number of electrons can accurately be tuned to N = 0,1,2 by an external gate voltage. Polarization, wave vector, and magnetic field dependent measurements enable us to clearly distinguish between resonant Raman and resonant photoluminescence processes. The Raman spectra for N = 1 and 2 electrons considerably differ from each other. In particular, for N = 2, the quantum-dot He, the spectra exhibit both singlet and triplet transitions reflecting the elementary many-particle interaction. Also the resonant photoluminescence spectra are significantly changed by varying the number of electrons in the QDs. For N = 1 we observe complex spectra possibly induced by strong polaronic effects that are suppressed for N = 2.

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“…RILS is proven to be a very powerful spectroscopy method to investigate collective modes of photogenerated electron-hole plasma in GaAs [35] , to study charge and spin excitations as well as to explore quantum phase transitions and the nature of quantum phases in a variety of quantum systems such as electron bilayers [15,16] , quantum Hall [36] and fractional quantum Hall effect systems [37,38] . Furthermore, collective excitations in quantum wires [39][40][41] , quantum dots [42,43] in dilute two-dimensional electron systems [44] and the spin-splitting in the hole dispersion [45] have been studied by RILS. Generally, collective excitations of the photogenerated exciton ensembles are expected to serve as a unique fingerprint to unambiguously identify the individual states in the phase diagram of dipolar exciton ensembles.…”

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confidence: 99%

Collective electronic excitation in a trapped ensemble of photogenerated dipolar excitons and free holes revealed by inelastic light scattering

et al. 2017

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Photogenerated excitonic ensembles confined in coupled GaAs quantum wells are probed by a complementary approach of emission spectroscopy and resonant inelastic light scattering.Lateral electrostatic trap geometries are used to create dense systems of spatially indirect excitons and excess holes with similar densities in the order of 10 11 cm -2. Inelastic light scattering spectra reveal a very sharp low-lying collective mode that is identified at an energy of 0.44 meV and a FWHM of only ~50 µeV. This mode is interpreted as a plasmon excitation of the excess hole system coupled to the photogenerated indirect excitons. The emission energy of the indirect excitons shifts under the application of a perpendicular applied electric field with the quantum-confined Stark effect unperturbed from the presence of free charge carriers. Our results illustrate the potential of studying low-lying collective excitations in photogenerated exciton systems to explore the many-body phase diagram, related phase transitions, and interaction physics. [1] . BEC has been observed for the first time in atomic systems [2,3] and later also in more exotic solid-state systems like exciton-polaritons [4][5][6] . Already more than 50 years ago, BEC has been predicted for excitons in semiconductors [7] . Most of such experiments are based on two tunnelcoupled semiconductor quantum wells (CQWs) hosting the excitons. These are electron-hole pairs coupled by the attractive Coulomb interaction. The bosonic quasiparticles exhibit a rich quantum phase diagram including a free exciton gas at elevated temperatures and low densities, which is expected to condense into a BEC with a macroscopic coherence at low temperatures.At high densities, an electron-hole plasma is predicted at higher temperatures that undergoes a Bardeen-Cooper-Schrieffer (BCS) transition to an excitonic insulator at low temperatures [1] .Also, signatures for a (classical) exciton liquid formed by repulsive exciton interactions have been reported [8] . The phase transition between the different phases might be gradual, and the coexistence of different (classical and quantum) phases is possible. Each phase inherently holds a characteristic spectrum of low energy collective excitations of strongly or weakly coupled electron-hole pairs including phenomena such as roton instabilities in their wave vector dispersion [9,10] . In this context, it has been shown for electron bilayers at a total filling factor of one, where exciton condensation occurs [11][12][13][14] , that deep and soft magnetorotons as well as collective spin excitations exist [15,16] . These excitations are linked to quantum phase transitions [15,16] .In general, there are two types of CQW systems hosting excitons. In one case, both CQWs are doped with electrons, and a strong perpendicular magnetic field is applied such that in each quantum well, the lowest Landau level is exactly half filled with electrons and consequently also half filled with holes. If the Coulomb interaction is strong enough in such CQWs, the...

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Resonant Raman Transitions into Singlet and Triplet States in InGaAs Quantum Dots Containing Two Electrons

Cited by 17 publications

References 23 publications

Transport spectroscopy of non-equilibrium many-particle spin states in self-assembled quantum dots

Transport spectroscopy of non-equilibrium many-particle spin states in self-assembled quantum dots

Elementary excitations in charge-tunable InGaAs quantum dots studied by resonant Raman and resonant photoluminescence spectroscopy

Collective electronic excitation in a trapped ensemble of photogenerated dipolar excitons and free holes revealed by inelastic light scattering

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