Moiré modulation of bulk electronic structures in CuxTiSe2-based mixed two- and three-dimensional heterostructures

Moir\'e superlattices provide a striking tool to controllably engineer electronic structures and realize various exotic quantum phenomena in two-dimensional (2D) systems. Surprisingly, moir\'e potential has recently been reported to extend its influence into three-dimensional (3D) graphitic thin films. Here, using angle-resolved photoemission spectroscopy, we report that 3D electronic states of transition-metal dichalcogenides (TMDs) can be modulated by interfacial moir\'e potential. The bulk electronic states of $\mathrm{C}{\mathrm{u}}_{x}\mathrm{TiS}{\mathrm{e}}_{2}$ unambiguously exhibit moir\'e clones due to the lattice mismatch with the noble-gas monolayer atop. We demonstrate that the interfacial moir\'e effect strongly couples with charge ordering with 3D wave vectors, which plays an important role in the formation of the mixed-dimensional moir\'e effect. We further exclude the final-state diffraction mechanism for the observed replicas. The moir\'e period can be further in situ tuned by different noble-gas atoms and annealing temperatures. Our results broaden the horizon of the mixed-dimensional moir\'e family from graphitic systems to TMD-based heterostructures and shed light on constructing functional devices based on versatile 2D-3D mixed-dimensional heterostructures.