Emergent Moiré Pattern from Substrate Strain in Heterostructure of PdTe₂/Bi₂Se₃

Topological superconductivity is a highly sought-after phenomena in condensed matter due to the possibility of such novel electronic states hosting massless Majorana fermions. One avenue to realize topological superconductivity is inducing superconductivity (SC) in a topological insulator (TI) via proximity effect with a s-wave superconductor. Via the method of Molecular Beam Epitaxy (MBE), growing ultra-thin heterostructures to proximitize superconductivity with topological surface states has become much easier while also being much more useful in device applications. This method, however, involves substantial interplay between the substrate and growth, which can lead to unique phenomena such as Moiré patterns. Here we report the growth of Type-II Dirac semimetal and superconductor PdTe2 on the TI Bi2Se3. We observe a Moiré pattern whose periodicity is larger than that caused by a lattice mismatch between the conventional lattices. The period of the Moiré pattern decreases with each additional layer grown. This indicates that the periodicity of the substrate causes significant strain to the crystal and a thickness dependent lattice expansion.