Abstract
Monolayer semiconducting transition metal dichalcogenides possess broken inversion symmetry and strong spin-orbit coupling, leading to a unique spin-valley locking effect. In 2H stacked pristine multilayers, spin-valley locking yields an electronic superlattice structure, where alternating layers correspond to barriers and quantum wells depending on the spin-valley indices. Here we show that the spin-valley locked superlattice hosts a kind of dipolar exciton with the electron and hole constituents separated in an every-other-layer configuration: that is, either in two even or two odd layers. Such excitons become optically bright via hybridization with intralayer excitons. This effect is also manifested by the presence of multiple anti-crossing patterns in the reflectance spectra, as the dipolar exciton is tuned through the intralayer resonance by an electric field. The reflectance spectra further reveal an excited state orbital of the every-other-layer exciton, pointing to a sizable binding energy in the same order of magnitude as the intralayer exciton. As layer thickness increases, the dipolar exciton can form a one-dimensional Bose–Hubbard chain displaying layer number-dependent fine spectroscopy structures.
Original language | English |
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Pages (from-to) | 501-506 |
Number of pages | 6 |
Journal | Nature Nanotechnology |
Volume | 18 |
Issue number | 5 |
DOIs | |
State | Published - May 2023 |
Funding
This work was mainly supported by DoE BES (DE-SC0018171). Sample fabrication and PFM characterization were partially supported by the ARO MURI programme (W911NF-18-1-0431). The atomic force microscope-related measurements were performed using instrumentation supported by the US National Science Foundation through the UW Molecular Engineering Materials Center, a Materials Research Science and Engineering Center (DMR-1719797). W.Y. and C.X. acknowledge support from the University Grant Committee/Research Grants Council of Hong Kong SAR (AoE/P-701/20 and HKU SRFS2122-7S05). W.Y. also acknowledges support from the Tencent Foundation. Bulk WSe crystal growth and characterization by J.Y. were 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 (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. 2