Probing moire excitons in MoSe2/WSe2 heterobilayers by combined micro-photoluminescence and lateral force microscopy
L. Caussou, H. Moutaabbid, M. Bernard, F. Margaillan, T. Taniguchi, K. Watanabe, C. Lagoin, F. Dubin, V. Voliotis
TL;DR
This work demonstrates that moiré-confined interlayer excitons in MoSe$_2$/WSe$_2$ heterobilayers can be probed and understood through a combined approach of lateral force microscopy (LFM) and micro-photoluminescence (PL). By fabricating and characterizing samples with twist angles around a few degrees, the authors reveal a continuous, regular moiré lattice with a period near $a_m\approx 9$ nm over diffraction-limited regions, and show that optimized interface adhesion via AFM ironing enhances exciton confinement and simplifies the PL to a small set of narrow lines. The authors build a concrete tight-binding (Bose-Hubbard) description for moiré excitons, deriving Wannier states and closest-neighbor hopping in a 1D sinusoidal moiré potential $V(x)=V_0\sin^2(Qx)$ with $Q=\pi/a_m$ and $V_0\approx 30$ meV, and connecting WS energies to observed PL peaks as $a_m$ varies from 6 to 11 nm. This framework supports controlled exploration of Bose-Hubbard physics, with the potential to realize Mott-like phases of interlayer excitons in engineered moiré lattices for quantum simulation in solid-state platforms.
Abstract
We study interlayer excitons in MoSe2/WSe2 heterobilayers, by combining lateral force microscopy and micro-photoluminescence spectroscopy. This allows us to correlate the spatial profile of the moiré superlattice with the distribution of optically active states accessible to interlayer excitons. In heterostructures where a few degrees twist angle is imposed between the MoSe and WSe crystallographic axes, we show that a continuous moiré lattice is realized across areas close to the optical diffraction limit. In such regions, the photoluminescence reduces to a few narrow-band lines only, energetically distributed consistently with the geometry of the moiré lattice. This correlation reveals that interlayer excitons explore a controlled periodic confinement, paving the way towards implementations of Bose-Hubbard models.