Abstract
Moiré excitons are emergent optical excitations in two-dimensional semiconductors with moiré superlattice potentials. Although these excitations have been observed on several platforms, a system with dynamically tunable moiré potential to tailor their properties is yet to be realized. Here we present a continuously tunable moiré potential in monolayer WSe2, enabled by its proximity to twisted bilayer graphene (TBG) near the magic angle. By tuning local charge density via gating, TBG provides a spatially varying and dynamically tunable dielectric superlattice for modulation of monolayer WSe2 exciton wave functions. We observed emergent moiré exciton Rydberg branches with increased energy splitting following doping of TBG due to exciton wave function hybridization between bright and dark Rydberg states. In addition, emergent Rydberg states can probe strongly correlated states in TBG at the magic angle. Our study provides a new platform for engineering moiré excitons and optical accessibility to electronic states with small correlation gaps in TBG.
| Original language | English |
|---|---|
| Pages (from-to) | 224-229 |
| Number of pages | 6 |
| Journal | Nature Materials |
| Volume | 23 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 2024 |
Funding
We thank J. L. Li and H. Yu for helpful discussions. This work was supported mainly by the US Department of Energy Basic Energy Sciences under award no. DE-SC0018171 (to X.X., M.H. and J.C.). Sample fabrication was partially supported by the ARO MURI programme (grant no. W911NF-18-1-0431 to M.H.). Electrical transport measurement was partially supported by the US National Science Foundation through the UW Molecular Engineering Materials Center, a Materials Research Science and Engineering Center (no. DMR-1719797 to X.X. and M.Y.). STM/spectroscopy measurement is supported by the Center on Programmable Quantum Materials, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences, under award no. DE-SC0019443 (to A.P. and E.S.). Work at the University of Hong Kong is supported by the Research Grants Council of Hong Kong SAR (nos. AoE/P-701/20 and HKU SRFS2122-7S05 to W.Y. and H.Z.). W.Y. also acknowledges support by the New Cornerstone Science Foundation. K.W. and T.T. acknowledge support from JSPS KAKENHI (grant nos. 19H05790, 20H00354 and 21H05233). X.X. acknowledges support from the State of Washington-funded Clean Energy Institute and from the Boeing Distinguished Professorship in Physics.