Abstract
Moiré superlattices of layered transition metal dichalcogenides are proven to host periodic electron crystals due to strong correlation effects. These electron crystals can also be intertwined with intricate magnetic phenomena. In this Letter, we present our findings on the moiré exchange effect, resulting from the modulation of local magnetic moments by electron crystals within well-aligned WSe2/WS2 heterobilayers. Employing polarization-resolved magneto-optical spectroscopy, we unveil a high-energy excitonic resonance near one hole per moiré unit cell (v=-1), which possesses a giant g factor several times greater than the already very large g factor of the WSe2 A exciton in this heterostructure. Supported by continuum model calculations, these high-energy states are found to be dark excitons brightened through Umklapp scattering from the moiré mini-Brillouin zone. When the carriers form a Mott insulating state near v=-1, the Coulomb exchange between doped carriers and excitons forms an effective magnetic field with moiré periodicity. This moiré exchange effect gives rise to the observed giant g factor for the excitonic Umklapp state.
| Original language | English |
|---|---|
| Article number | 086501 |
| Journal | Physical Review Letters |
| Volume | 133 |
| Issue number | 8 |
| DOIs | |
| State | Published - Aug 23 2024 |
Funding
This work was mainly supported by DOE BES under Award No. DE-SC0018171. Sample fabrication and PFM characterization are partially supported by ARO MURI program (Grant No. W911NF-18-1-0431). The atomic force microscope-related measurements were performed using instrumentation supported by the U.S. National Science Foundation through the UW Molecular Engineering Materials Center (MEM·C), a Materials Research Science and Engineering Center (DMR-2308979). W. Y. acknowledges support by the Research Grants Council of Hong Kong SAR (AoE/P-701/20, HKU SRFS2122-7S05). Bulk crystal growth and characterization by J. Y. is supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. K. W. and T. T. acknowledge support from the JSPS KAKENHI (Grants No. 20H00354 and No. 23H02052) and World Premier International Research Center Initiative (WPI), MEXT, Japan. X. X. acknowledges support from the State of Washington funded Clean Energy Institute and from the Boeing Distinguished Professorship in Physics.