Coherent Coupling of Excitons and Trions in a Photoexcited CdTe/CdMgTe Quantum Well

Moody, Galan; Акимов, И. А.; Li, Hebin; Singh, Rohan; Yakovlev, D. R.; Karczewski, G.; Wiater, M.; Wójtowicz, T.; Bayer, М.; Cundiff, Steven T.

doi:10.1103/physrevlett.112.097401

Cited by 52 publications

(48 citation statements)

References 40 publications

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“…For example, ∆ ≈ 4 meV observed here is at least an order of magnitude larger compared to exciton-trion coupling in a 20-nmwide n-doped CdTe/CdMgTe quantum well [32]. Strong exciton-trion coherent coupling makes TMDs an excellent platform for opto-electronic devices designed for a variety of coherent spin phenomena and conditional control schemes for quantum information applications.…”

Section: Fig 2 (Color Online) (A) Two-dimensional Spectrum Featurinmentioning

confidence: 95%

“…Since the lower transitions (|0 ↔ |1 and |0 ↔ |2 ) are excited by the optical field to first order in perturbation theory, while the upper transitions (|1 ↔ |3 and |2 ↔ |3 ) contribute to third order only if the lower transitions have been excited, the electronic and optical properties of the upper transitions dictate the interaction strength [30]. Specifically, we consider excitation-induced shift (EIS) and excitation-induced dephasing (EID) effects, which have been used to explain coherent exciton coupling in semiconductor quantum wells [31,32] and quantum dots [33,34]. EIS and EID correspond to the real and imaginary part of the renormalization energy when interaction effects are considered, thus both effects must appear simultaneously, in principle.…”

Section: Fig 2 (Color Online) (A) Two-dimensional Spectrum Featurinmentioning

confidence: 99%

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Coherent Electronic Coupling in Atomically ThinMoSe2

et al. 2014

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We report the first direct spectroscopic evidence for coherent electronic coupling between excitons and trions in atomically thin transition metal dichalcogenides, specifically monolayer MoSe2. Signatures of coupling appear as isolated cross-peaks in two-color pump-probe spectra, and the lineshape of the peaks reveals that the coupling originates from many-body interactions. Excellent agreement between the experiment and density matrix calculations suggests the formation of a correlated exciton-trion state due to their coupling. PACS numbers: 73.20.Mf,78.47.jg Atomically thin transition metal dichalcogenides (TMDs) have emerged as an interesting class of twodimensional materials due to their unique optical properties. For example, some materials (e.g. MoS 2 ) exhibit a crossover from an indirect-to-direct gap semiconductor as the material thickness is reduced to one atomic layer [1], consequently enhancing the photoluminescence efficiency [2]. Valley-specific optical selection rules [3][4][5] dictated by time reversal and spatial inversion symmetries in monolayer structures have been observed, and such selection rules have been electrically controlled in bilayers [6]. These attributes make TMDs particularly intriguing for tunable and flexible valleytronic and photonic devices [7].A striking feature in the linear optical spectra of atomically thin TMDs is the presence of pronounced exciton resonances (Coulomb-bound electron-hole pairs), even at room temperature. The large binding energy of excitons, estimated to be hundreds of meV [8,9], as well as tightlybound trions (an exciton bound with an extra electron or hole) [10,11] arises from reduced dielectric screening in the thickness direction of the film [12]. It is reasonable to speculate that enhanced Coulomb interactions responsible for the large exciton and trion binding energies should also lead to strong coherent coupling among these quasiparticles. The presence or absence of coupling between excitonic states in conventional semiconductors is known to significantly influence energy transfer [13], photon emission statistics [14], and quantum-logic operations [15] in quantum wells, wires, and dots. It is particularly imperative to understand the properties of these intrinsically many-body states in TMDs as they are inevitably present in all optical devices such as photovoltaics [16,17], detectors [18], and modulators [19,20].The existence and manifestation of electronic coupling is challenging to study experimentally since nonlinear spectroscopy techniques are required. Previous experiments thus far have provided limited information on the effects of phase-space filling, exciton-carrier broadening effects [21,22], inter-excitonic scattering [23], valley relaxation dynamics [24], and biexciton formation [25] in TMDs.In this Letter, we provide clear evidence for coherent exciton-trion interactions in monolayer MoSe 2 using twocolor ultrafast pump-probe spectroscopy. In a high quality sample with spectrally well-resolved exciton and trion resonances, spectrosc...

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Section: Fig 2 (Color Online) (A) Two-dimensional Spectrum Featurinmentioning

confidence: 95%

Section: Fig 2 (Color Online) (A) Two-dimensional Spectrum Featurinmentioning

confidence: 99%

Coherent Electronic Coupling in Atomically ThinMoSe2

et al. 2014

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“…The extra dimension, given by the excitation frequency axis, yields 2D spectra where discrimination of specific features (otherwise overlapped in 1D methods) is now possible [1]. Consequently, 2D-ES has provided new insights into topics as diverse as quantum phenomena in biology [2][3][4], energy transfer [5,6], singlet fission [7], nanomaterials [8,9], reaction dynamics [10][11][12], and many body effects in coupled quantum wells [13][14][15]. However, although 2D-ES greatly facilitates the discrimination of physical phenomena affecting electronic transitions such as line-broadening mechanisms, vibrational and electronic couplings, ambiguities remain in detailed analysis, especially for molecular systems where both vibrational and electronic couplings may play a role.…”

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confidence: 99%

Resolving Vibrational from Electronic Coherences in Two-Dimensional Electronic Spectroscopy: The Role of the Laser Spectrum

et al. 2017

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The observation of coherent quantum effects in photosynthetic light-harvesting complexes prompted the question whether quantum coherence could be exploited to improve the efficiency in new energy materials. The detailed characterization of coherent effects relies on sensitive methods such as two-dimensional electronic spectroscopy (2D-ES). However, the interpretation of the results produced by 2D-ES is challenging due to the many possible couplings present in complex molecular structures. In this work, we demonstrate how the laser spectral profile can induce electronic coherencelike signals in monomeric chromophores, potentially leading to data misinterpretation. We argue that the laser spectrum acts as a filter for certain coherence pathways and thus propose a general method to differentiate vibrational from electronic coherences.

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“…The timing of conjugated pulse A in the sequence can be changed to arrive second to access non-rephasing (or S II ) signal or third to access two-quantum (or S III ) signal. [26][27][28][29][30] The radiated FWM field is interfered with a local oscillator pulse for phase resolution and is spectrally resolved by a spectrometer. The spectral interference is detected using a CCD camera.…”

Section: A Experimental Setupmentioning

confidence: 99%

Multi-dimensional coherent optical spectroscopy of semiconductor nanostructures: Collinear and non-collinear approaches

Nardin

Autry

Singh

et al. 2015

Journal of Applied Physics

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We review our recent work on multi-dimensional coherent optical spectroscopy (MDCS) of semiconductor nanostructures. Two approaches, appropriate for the study of semiconductor materials, are presented and compared. A first method is based on a non-collinear geometry, where the Four-Wave-Mixing (FWM) signal is detected in the form of a radiated optical field. This approach works for samples with translational symmetry, such as Quantum Wells (QWs) or large and dense ensembles of Quantum Dots (QDs). A second method detects the FWM in the form of a photocurrent in a collinear geometry. This second approach extends the horizon of MDCS to sub-diffraction nanostructures, such as single QDs, nanowires, or nanotubes, and small ensembles thereof. Examples of experimental results obtained on semiconductor QW structures are given for each method. In particular, it is shown how MDCS can assess coupling between excitons confined in separated QWs.

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Coherent Coupling of Excitons and Trions in a Photoexcited CdTe/CdMgTe Quantum Well

Cited by 52 publications

References 40 publications

Coherent Electronic Coupling in Atomically ThinMoSe2

Coherent Electronic Coupling in Atomically ThinMoSe2

Resolving Vibrational from Electronic Coherences in Two-Dimensional Electronic Spectroscopy: The Role of the Laser Spectrum

Multi-dimensional coherent optical spectroscopy of semiconductor nanostructures: Collinear and non-collinear approaches

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