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Abstract Applying lattice strain to thin films, a critical factor to tailor their properties such as stabilizing a structural phase unstable at ambient pressure, generally necessitates heteroepitaxial growth to control the lattice mismatch with substrate. Therefore, while homoepitaxy, the growth of thin film on a substrate made of the same material, is a useful method to fabricate high‐quality thin films, its application to studying strain‐induced structural phases is limited. Contrary to this general belief, here the quasi‐homoepitaxial growth of Cs and Rb thin films is reported with substantial in‐plane compressive strain. This is achieved by utilizing the alkali‐metal layer existing in bulk crystal of kagome metals AV3Sb5 (A = Cs and Rb) as a structural template. The angle‐resolved photoemission spectroscopy measurements reveal the formation of metallic quantum well states and notable thickness‐dependent quasiparticle lifetime. Comparison with density functional theory calculations suggests that the obtained thin films crystalize in the face‐centered cubic structure, which is typically stable only under high pressure in bulk crystals. These findings provide a useful approach for synthesizing highly strained thin films by quasi‐homoepitaxy, and pave the way for investigating many‐body interactions in Fermi liquids with tunable dimensionality.

Abstract A current key challenge in 2D materials is the realization of emergent quantum phenomena in hetero structures via controlling the moiré potential created by the periodicity mismatch between adjacent layers, as highlighted by the discovery of superconductivity in twisted bilayer graphene. Generally, the lattice structure of the original host material remains unchanged even after the moiré superlattice is formed. However, much less attention is paid for the possibility that the moiré potential can also modify the original crystal structure itself. Here, it is demonstrated that octahedral MoTe2 which is unstable in bulk is stabilized in a commensurate MoTe2/graphene hetero‐bilayer due to the moiré potential created between the two layers. It is found that the reconstruction of electronic states via the moiré potential is responsible for this stabilization, as evidenced by the energy‐gap opening at the Fermi level observed by angle‐resolved photoemission and scanning tunneling spectroscopies. The present results provide a fresh approach to realize novel 2D quantum phases by utilizing the moiré potential.