Ultrafast Transition from Intra- to Interlayer Exciton Phases in a Van Der Waals Heterostructure

Merkl, Philipp; Mooshammer, Fabian; Steinleitner, Philipp; Girnghuber, Anna; Lin, Kai-Qiang; Nagler, Philipp; Höller, Johannes; Schüller, Christian; Lupton, John M.; Korn, Tobias; Ovesen, Simon; Brem, Samuel; Malić, Ermin; Huber, Rupert

doi:10.1364/cleo_at.2019.jth5c.6

Cited by 4 publications

(4 citation statements)

References 9 publications

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“…Thus, we find roughly a = 9.2 Å and b = 3.1 Å. It may be noted that a model describing van der Waals heterostructures as homogeneous material slabs separated by vacuum regions has recently successfully explained exciton binding energies in such geometries [40]. For MoS 2 and other TMDs, the barrier for conduction band electrons can be estimated as the vacuum level relative to the conduction band minimum, i.e., the electron affinity V 0 ≈ 3.8 eV [41].…”

Section: Structuresupporting

confidence: 62%

Giant Stark effect in coupled quantum wells: Analytical model

Pedersen

2019

Phys. Rev. B

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Coupled quantum wells have been proposed as candidates for highly polarizable structures due to their neardegenerate and dipole-coupled electronic states. Hence, many interesting applications in linear and nonlinear optics can be envisioned. We analyze this proposal considering a simple structure with a delta-function barrier separating the wells. While very substantial Stark shifts are certainly predicted for this geometry, perturbative estimates based on polarizabilities (and hyperpolarizabilities) fail beyond a critical field strength that depends inversely on the barrier. Hence, a giant Stark effect due to near-degenerate states is invariably limited by a small critical field. Our analytical (hyper) polarizability expressions are applied to find quantitative Stark shifts for GaAs quantum wells and transition-metal dichalcogenide bilayers. The predicted Stark shifts and critical fields agree with the field dependence observed in a range of available experiments.

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Section: Structuresupporting

confidence: 62%

Giant Stark effect in coupled quantum wells: Analytical model

Pedersen

2019

Phys. Rev. B

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“…or by using means like strong magnetic field [66,67] , and unusual experimental geometries [68] . From the perspective of dynamics, the ability of optical spectroscopy to probe only 'bright' transitions leads to sparse mapping in momentum-space of various scattering processes of charge-carriers and excitons (e.g., two bright excitons that are perturbed at the beginning and the end of charge-transfer process [69] , or some internal excitations of these excitons [70] ). Figure 4a illustrates the distributions of these various excitonic states across the BZ and highlights the distributions and dynamic processes that momentum-resolved spectroscopy can effectively investigate.…”

Section: Virtues Of Momentum-resolved Versus Optical Characterization...mentioning

confidence: 99%

Through the Lens of a Momentum Microscope: Viewing Light‐Induced Quantum Phenomena in 2D Materials

2022

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Van der Waals (vdW) materials at their two-dimensional limit are diverse, flexible, and unique laboratories to study fundamental quantum phenomena and their future applications. Their novel properties rely on their pronounced Coulomb interactions, variety of crystal symmetries and spinphysics, and the ease of incorporation of different vdW materials to form sophisticated heterostructures. In particular, the excited state properties of many two-dimensional semiconductors and semi-metals are relevant for their technological applications, particularly those that can be induced by light. In this paper, we review the recent advances made in studying out-of-equilibrium, light-induced, phenomena in these materials using powerful, surface-sensitive, time-resolved photoemission-based techniques, with a particular emphasis on the emerging multi-dimensional photoemission spectroscopy technique of time-resolved momentum microscopy. We discuss the advances this technique has enabled in studying the nature and dynamics of occupied excited states in these materials. Then, we project for the future research directions opened by these scientific and instrumental advancements, studying the physics of two-dimensional materials and the opportunities to engineer their band-structure and band-topology by laser fields.

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“…The interlayer excitons (IXs) are formed by bound pairs of electrons and holes spatially separated in two different two-dimensional (2D) semiconductor materials of van der Waals heterostructures (vdWHs) [1][2][3][4][5][6][7][8][9][10][11][12], such as those in 2D transition metal dichalcogenides (TMDC) bilayer with a type-II band alignment. The spatial separation between the electron and hole allows achieving long IX lifetimes, orders of magnitude longer than lifetimes of intralayer excitons in TMDC monolayers [8,11,[13][14][15][16][17][18]. This longer lifetime, combined with the large binding energy, has enabled the exploration of the rich many-body physics of IX and their applications in tunable photonic and optoelectronic devices [8,17,[19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Self-trapped interlayer excitons in van der Waals heterostructures

Deng¹,

Li²,

Ma³

et al. 2021

Preprint

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The self-trapped state (STS) of interlayer exciton (IX) has been aroused enormous interesting owing to their significant impact on the fundamental properties of the van der Waals heterostructures (vdWHs). Nevertheless, the microscopic mechanisms of STS are still controversial. Herein, we study the corrections of the binding energies of the IXs due to the exciton-interface optical phonon coupling in four kinds of vdWHs and find that these IXs are in the STS for the appropriate ratio of the electron and hole effective masses. We show that these STSs could be classified into the type I with the increasing binding energy in the tens of meV range, which are very agreement with the red-shift of the IXs spectra in experiments, and the type II with the decreasing binding energy, which provides a possible explanation for the blue-shift and broad linewidth of the IX's spectra in the low temperature. Moreover, these two types of self-trapped IXs could be transformed into each other by adjusting the structural parameters of vdWHs. These results not only provide an in-depth understanding for the self-trapped mechanism of IX, but also shed light on the modulations of IXs in vdWHs.

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Ultrafast Transition from Intra- to Interlayer Exciton Phases in a Van Der Waals Heterostructure

Cited by 4 publications

References 9 publications

Giant Stark effect in coupled quantum wells: Analytical model

Giant Stark effect in coupled quantum wells: Analytical model

Through the Lens of a Momentum Microscope: Viewing Light‐Induced Quantum Phenomena in 2D Materials

Self-trapped interlayer excitons in van der Waals heterostructures

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