Epitaxial Growth of Topological Insulator Bi₂Se₃ Thin Films on the Quantum Spin Liquid Candidate α-RuCl₃ by Molecular Beam Epitaxy

Heterostructures with topological insulators (TIs) serve as a breeding ground for novel states of matter; various classes of materials ranging from semiconductors to magnets and superconductors have been combined with TIs. Quantum spin liquids (QSLs) have also been brought into focus as a new topological material. However, TI/QSL heterostructure, a stage where the two different electronic states can compete, coexist, and collaborate, has remained unexplored. Heteroepitaxial growth, one of the most promising methods of preparing uniform materials with well-defined structural properties, is an essential step in investigating emerging physical phenomena in real TI/QSL heterostructures. Here, we present the epitaxial growth of Bi₂Se₃ thin films on α-RuCl₃ layers using MBE and their structural characteristics. The films with an atomically smooth and uniform surface were prepared through the two-step growth process and examined by AFM. We found, using TEM investigation, a well-defined epitaxial relationship between Bi₂Se₃ and α-RuCl₃ and the formation of commensurate supercells despite a lattice misfit of –60%, which is attributed to the weak van der Waals interaction on the interface. We believe that our work opens the door to further exploration of the physics of the heterostructure.