Ten-valley excitonic complexes in charge-tunable monolayer WSe2
Exotic six- and eight-particle excitonic complexes have recently been discovered in two-dimensional (2D) semiconductors. This study reveals a stable many-body exciton in WSe2 formed by 20 interacting quasiparticles, which appears when strong electrostatic doping fills the Q valley.
Excitons in 2D Semiconductors
Excitons play a crucial role in the optical properties of 2D semiconductors. Strong particle interactions lead to unique excitonic complexes, offering a valuable platform for testing exciton and quantum many-body theories.
Discovery of a New Many-body Exciton
The authors report a previously unobserved many-body exciton emerging when both the K and Q valleys in WSe2 are filled. By using charge-tunable devices with ultrathin dielectrics, doping levels reach several 1013 cm−2, enabling detailed optical probing of the exciton landscape.
Stable Complex Formation
They observe the formation of a thermodynamically stable complex once 10 valleys are electrostatically filled.
"Our results are well-described by a model where the number of distinguishable Fermi seas interacting with the photoexcited electron-hole pair defines the complex’s behavior."
Insights from Magneto-optical Measurements
Magneto-optical experiments provide deeper understanding of the complex’s physics and confirm its many-body nature.
Significance and Implications
This discovery not only broadens the known range of excitons in 2D semiconductors but also offers a new tool to test exciton models and address open questions related to screened Coulomb interactions in these materials.
Layered semiconductors and their heterostructures are rich in tightly bound exciton complexes, which enhance light-matter interactions.
"Layered semiconductors and their heterostructures host a plethora of tightly bound exciton complexes, which define enhanced light-matter couplings."
Author’s Summary
A groundbreaking many-body exciton with 20 interacting quasiparticles emerges in WSe2 under strong doping, expanding the understanding of excitonic phenomena in 2D semiconductors.