Electrical control of hybrid exciton transport in a van der Waals heterostructure

Nature Photonics, Journal Year: 2023, Volume and Issue: 17(7), P. 615 - 621

Published: April 20, 2023

Interactions between out-of-plane dipoles in bosonic gases enable the long-range propagation of excitons. The lack direct control over collective dipolar properties has so far limited degrees tunability and microscopic understanding exciton transport. In this work we modulate layer hybridization interplay many-body interactions excitons a van der Waals heterostructure with an applied vertical electric field. By performing spatiotemporally resolved measurements supported by theory, uncover dipole-dependent transport different hybridization. Moreover, find constant emission quantum yields transporting species as function excitation power radiative decay mechanisms dominating nonradiative ones, fundamental requirement for efficient excitonic devices. Our findings provide complete picture effects dilute gases, have crucial implications studying emerging states matter such Bose-Einstein condensation optoelectronic applications based on propagation.

Language: Английский

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Two-Dimensional Transition Metal Dichalcogenides: A Theory and Simulation Perspective

Chemical Reviews, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 2, 2025

Two-dimensional transition metal dichalcogenides (2D TMDs) are a promising class of functional materials for fundamental physics explorations and applications in next-generation electronics, catalysis, quantum technologies, energy-related fields. Theory simulations have played pivotal role recent advancements, from understanding physical properties discovering new to elucidating synthesis processes designing novel devices. The key has been developments ab initio theory, deep learning, molecular dynamics, high-throughput computations, multiscale methods. This review focuses on how theory contributed progress 2D TMDs research, particularly twisted moiré-based TMDs, predicting exotic phases TMD monolayers heterostructures, nucleation growth synthesis, comprehending electron transport characteristics different contacts potential devices based heterostructures. notable achievements provided by highlighted, along with the challenges that need be addressed. Although demonstrated prototype created, we conclude highlighting research areas demand most attention simulation might address them aid attaining true toward commercial device realizations.

Language: Английский

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Probing electron-hole Coulomb correlations in the exciton landscape of a twisted semiconductor heterostructure

Science Advances, Journal Year: 2024, Volume and Issue: 10(6)

Published: Feb. 7, 2024

In two-dimensional semiconductors, cooperative and correlated interactions determine the material’s excitonic properties can even lead to creation of states matter. Here, we study fundamental two-particle exciton state formed by Coulomb interaction between single-particle holes electrons. We find that ultrafast transfer an exciton’s hole across a type II band-aligned semiconductor heterostructure leads unexpected sub-200-femtosecond upshift energy electron being photoemitted from state. While relaxation usually energetic downshift spectroscopic signature, show this is clear fingerprint parts exciton. way, time-resolved photoelectron spectroscopy straightforwardly established as powerful method access electron-hole correlations behavior in quantum materials. Our work highlights capability motivates future optically inaccessible electronic

Language: Английский

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Quadrupolar excitons in MoSe2 bilayers

Nature Communications, Journal Year: 2025, Volume and Issue: 16(1)

Published: Feb. 5, 2025

Abstract The quest for platforms to generate and control exotic excitonic states has greatly benefited from the advent of transition metal dichalcogenide (TMD) monolayers their heterostructures. Among unconventional states, quadrupolar excitons—a superposition two dipolar excitons with anti-aligned dipole moments—are great interest applications in quantum simulations investigation many-body physics. Here, we unambiguously demonstrate emergence natural MoSe 2 homobilayers, whose energy shifts quadratically electric field. In contrast trilayer systems, homobilayers have many advantages, which include a larger coupling between excitons. Our experimental observations are complemented by many-particle theory calculations offering microscopic insights formation results suggest TMD as ideal platform engineering interaction light thus candidate carrying out on-chip simulations.

Language: Английский

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Bosonic Delocalization of Dipolar Moiré Excitons

Nano Letters, Journal Year: 2023, Volume and Issue: 23(10), P. 4627 - 4633

Published: May 15, 2023

In superlattices of twisted semiconductor monolayers, tunable moiré potentials emerge, trapping excitons into periodic arrays. particular, spatially separated interlayer are subject to a deep potential landscape and they exhibit permanent dipole providing unique opportunity study interacting bosonic lattices. Recent experiments have demonstrated density-dependent transport properties excitons, which could play key role for technological applications. However, the intriguing interplay between exciton-exciton interactions has not been well understood yet. this work, we develop microscopic theory in external allowing us tackle highly challenging problem. We find that lead delocalization at intermediate densities, show how transition can be tuned via twist angle temperature. The is accompanied by modification optical resonances, gradually merge single free exciton peak.

Language: Английский

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Trion Photoluminescence and Trion Stability in Atomically Thin Semiconductors

Physical Review Letters, Journal Year: 2024, Volume and Issue: 132(3)

Published: Jan. 17, 2024

The optical response of doped monolayer semiconductors is governed by trions, i.e. photoexcited electron-hole pairs bound to doping charges. While their photoluminescence (PL) signatures have been identified in experiments, a microscopic model consistently capturing bright and dark trion peaks still lacking. In this work, we derive generalized PL formula on quantum-mechanical footing, considering direct phonon-assisted recombination mechanisms. We show the energy landscape ${\mathrm{WSe}}_{2}$ solving Schr\"odinger equation. reveal that mass imbalance between equal charges results less stable trions exhibiting small binding and, interestingly, large energetic offset from exciton spectra. Furthermore, compute temperature-dependent spectra for $n$- $p$-doped monolayers predict yet unobserved originating with an electron at $\mathrm{\ensuremath{\Lambda}}$ point. Our work presents important step toward understanding internal structure determining stability fingerprint.

Language: Английский

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Electrical tuning of moiré excitons in MoSe₂ bilayers

2D Materials, Journal Year: 2022, Volume and Issue: 10(1), P. 014013 - 014013

Published: Dec. 7, 2022

Recent advances in the field of vertically stacked 2D materials have revealed a rich exciton landscape. In particular, it has been demonstrated that out-of-plane electrical fields can be used to tune spectral position spatially separated interlayer excitons. Other studies shown there is strong hybridization states, resulting from mixing electronic states both layers. However, connection between twist-angle dependent and field-induced energy shifts remained dark. Here, we investigate on microscopic footing interplay tuning moir\'e excitons MoSe$_2$ homobilayers. We reveal distinct regions PL spectra are clearly dominated by either intralayer or excitons, even dark Consequently, predict twist-angle-dependent critical at which material being transformed direct into an indirect semiconductor. Our work provides new insights experimentally accessible knobs significantly physics atomically thin nanomaterials.

Language: Английский

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Overcoming the Limitation of Spin Statistics in Organic Light Emitting Diodes (OLEDs): Hot Exciton Mechanism and Its Characterization

International Journal of Molecular Sciences, Journal Year: 2023, Volume and Issue: 24(15), P. 12362 - 12362

Published: Aug. 2, 2023

Triplet harvesting processes are essential for enhancing efficiencies of fluorescent organic light-emitting diodes. Besides more conventional thermally activated delayed fluorescence and triplet-triplet annihilation, the hot exciton mechanism has been recently noticed because it helps reduce efficiency roll-off improve device stability. Hot materials enable conversion triplet excitons to singlet ones via reverse inter-system crossing from high-lying states thereby depopulation long-lived that prone chemical and/or degradation. Although their anti-Kasha characteristics have not clearly explained, numerous molecules with behaviors assigned reported. Indeed, related developments appear just passed stage infancy now, there will likely be roles computational elucidations can play. With this perspective in mind, we review some selected experimental studies on designs then studies. On side, examine what found is still missing regard properly understanding interesting mechanism. We further discuss potential future points interests toward aiming eventually presenting silico design guides.

Language: Английский

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Ultrafast dynamics of bright and dark excitons in monolayer WSe₂ and heterobilayer WSe₂/MoS₂

2D Materials, Journal Year: 2023, Volume and Issue: 10(3), P. 035039 - 035039

Published: June 22, 2023

Abstract The energy landscape of optical excitations in mono- and few-layer transition metal dichalcogenides (TMDs) is dominated by optically bright dark excitons. These excitons can be fully localized within a single TMD layer, or the electron- hole-component exciton charge-separated over multiple layers. Such intra- interlayer have been characterized detail using all-optical spectroscopies, and, more recently, photoemission spectroscopy. In addition, there are so-called hybrid whose and/or delocalized two layers, therefore provide promising pathway to mediate charge-transfer processes across interface. Hence, an in-situ characterization their dynamics vital interest. this work, femtosecond momentum microscopy combined with many-particle modeling, we quantitatively compare momentum-indirect intralayer monolayer WSe 2 heterobilayer /MoS , draw three key conclusions: First, find that reduced when compared pure character. Second, show formed via exciton-phonon scattering from excited And third, demonstrate efficiency for phonon absorption emission strongly dependent on alignment respect exciton. Overall, our work provides microscopic insights into bilayers.

Language: Английский

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Impact of atomic reconstruction on optical spectra of twisted TMD homobilayers

Physical Review Materials, Journal Year: 2024, Volume and Issue: 8(3)

Published: March 4, 2024

Twisted bilayers of transition metal dichalcogenides (TMDs) have revealed a rich exciton landscape including hybrid excitons and spatially trapped moiré that dominate the optical response material. Recent studies shown in low-twist-angle regime, lattice undergoes significant relaxation order to minimize local stacking energies. Here, large domains low energy configurations emerge, deforming crystal lattices via strain consequently impacting electronic band structure. However, so far direct impact atomic reconstruction on properties has not been well understood. we apply microscopic material-specific approach predict change potential depth for reconstructed lattice, with most drastic occurring naturally stacked TMD homobilayers. We show appearance multiple flat bands position trapping sites compared rigid lattice. Most importantly, multipeak structure emerging absorption WSe2 homobilayers—in contrast single peak dominates This finding can be exploited as an unambiguous signature spectra twisted Published by American Physical Society 2024

Language: Английский

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