Rydberg states are widespread in various physical platforms such as atoms, molecules, and solids. In particular, Rydberg excitons are highly excited Coulomb-bound states of electron-hole pairs, first discovered in the semiconductor material Cu2Or in the 1950s.
In a study published in Sciencedr. Xu Yang and his colleagues from the Institute of Physics of the Chinese Academy of Sciences (CAS), in collaboration with researchers led by Dr. Yuan Shengjun of Wuhan University, reports observing Rydberg moiré excitons, trapped in moiré Rydberg excitons in monolayer semiconductor WSe2 adjacent to small angle twisted bilayer graphene (TBG).
The solid-state nature of Rydberg excitons, combined with their large dipole moments, strong mutual interactions and highly enhanced interactions with the environment, hold promise for a wide range of sensing applications, quantum optics, and quantum simulation.
However, researchers have not yet fully exploited the potential of Rydberg excitons. One of the main obstacles is the difficulty of efficiently trapping and manipulating Rydberg excitons. The rise of two-dimensional (2D) moiré superlattices with tunable periodic potentials provides a possible way forward.
In recent years, Dr. Xu Yang and his colleagues worked to explore the application of Rydberg excitons in 2D semiconducting transition metal dichalcogenides (such as WSe2). They developed a new Rydberg sensing technique that exploits the sensitivity of Rydberg excitons to the dielectric environment to detect exotic phases in nearby 2D electronic systems.
In this study, using low-temperature optical spectroscopy measurements, the researchers first found Rydberg moiré excitons that appear as multiple energy splittings, a pronounced red shift, and a narrow linewidth in the reflectance spectra. .
Using numerical calculations made by a group from Wuhan University, the researchers attributed these observations to the spatially varying charge distribution of TBG, which creates a periodic potential landscape (called moiré potential) for the interaction of Rydberg excitons.
The strong confinement of Rydberg excitons is achieved by largely unequal interlayer interactions of the constituent electron and hole of a Rydberg exciton due to the spatially accumulated charges centered in the AA-stacked regions of TBG. Rydberg moiré excitons thus realize electron-hole separation and exhibit the behavior of long-lived charge-transfer excitons.
Researchers have demonstrated a new method of manipulating Rydberg excitons, which is difficult to achieve in most semiconductors. The long-wavelength (tens of nm) moiré superlattice in this study serves as an analog to optical lattices produced by a standing-wave laser beam or arrays of optical tweezers used for Rydberg atom trapping.
In addition, tunable moiré wavelengths, in-situ electrostatic gating, and longer lifetimes all ensure good controllability of the system, with a strong light-matter interaction for convenient optical excitation and readout.
This study may provide new opportunities for realizing the next step in Rydberg–Rydberg interactions and parallel control of Rydberg states, with potential applications in quantum information processing and computing. quantum.
More information:
Qianying Hu et al, Observation of Rydberg moiré excitons, Science (2023). DOI: 10.1126/science.adh1506
Awarded by the Chinese Academy of Sciences
Citation: Scientists discover Rydberg moiré excitons (2023, July 4) retrieved on July 4, 2023 from https://phys.org/news/2023-07-scientists-rydberg-moir-excitons.html
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