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Abstract Excitons are elementary optical excitation in semiconductors. The ability to manipulate and transport these quasiparticles would enable excitonic circuits and devices for quantum photonic technologies. Recently, interlayer excitons in 2D semiconductors have emerged as a promising candidate for engineering excitonic devices due to their long lifetime, large exciton binding energy, and gate tunability. However, the charge-neutral nature of the excitons leads to weak response to the in-plane electric field and thus inhibits transport beyond the diffusion length. Here, we demonstrate the directional transport of interlayer excitons in bilayer WSe2driven by the propagating potential traps induced by surface acoustic waves (SAW). We show that at 100 K, the SAW-driven excitonic transport is activated above a threshold acoustic power and reaches 20 μm, a distance at least ten times longer than the diffusion length and only limited by the device size. Temperature-dependent measurement reveals the transition from the diffusion-limited regime at low temperature to the acoustic field-driven regime at elevated temperature. Our work shows that acoustic waves are an effective, contact-free means to control exciton dynamics and transport, promising for realizing 2D materials-based excitonic devices such as exciton transistors, switches, and transducers up to room temperature.
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Large excitonic effects in 2D Cs3Bi2I9-xClx perovskites
Two-dimensional Cs3Bi2I9 (2D CBI) belongs to a family of soft nanomaterials and has been previously shown to host large electrophotonic responses and optically addressable valley degrees of freedom governed by flat bands, large carrier effective masses, and quantum confinement [Phys. Rev. Mater. 7, 2, 024002 (2023)]. Using advanced ab initio methods, we show the evolution of the excitonic features of 2D CBI with isoelectronic substitution of iodine with chlorine: Cs3Bi2I9-xClx (0 ≤ x ≤ 9). Our calculations reveal a significant increase in the excitonic behavior with exciton binding energy Eb as high as 3.0 ± 0.2 eV. Such Eb is significantly larger than those reported in any 2D materials. Our analysis shows notable deviation from established binding energy scaling laws for generic 2D materials.
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- Award ID(s):
- 2202101
- PAR ID:
- 10501550
- Publisher / Repository:
- APS
- Date Published:
- Journal Name:
- Bulletin of the American Physical Society
- ISSN:
- 0003-0503
- Format(s):
- Medium: X
- Location:
- Minneapolis, MN
- Sponsoring Org:
- National Science Foundation
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