Combining various two-dimensional materials into van der Waals (vdW) heterostructures has been shown to lead to emergent quantum systems. A heterostructure composed of a vdW topological insulator (TI) such as ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ with a quantum spin liquid (QSL) such as $\alpha \text{−}{\mathrm{RuCl}}_3$ is of great interest for the potential for the chiral Dirac electrons in the TI surface states to interact strongly with the fractionalized fermionic spin excitations in the QSL. We report the heteroepitaxial growth of ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ thin films on $\alpha \text{−}{\mathrm{RuCl}}_3$ as well as the characterization of their structural and electrical properties. ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ thin films with an atomically smooth and uniform surface are grown by molecular beam epitaxy. The heterostructure exhibits a preferential epitaxial relationship corresponding to $\left(5\times 5\right)\text{–}{\mathrm{Bi}}_2{\mathrm{Se}}_3/(2\sqrt{3}\times 2\sqrt{3}$) $R{30}^{\circ }\text{–}\alpha \text{−}{\mathrm{RuCl}}_3$ commensurate supercells with a periodicity of 1.2 nm. The formation of the superlattice despite a lattice mismatch as large as 60% is attributed to the vdW heteroepitaxy. Magnetotransport measurements as a function of temperature show ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ films grown on $\alpha \text{−}{\mathrm{RuCl}}_3$ are heavily $n$-doped, $n_e\sim {10}^{14}\mathrm{c}{\mathrm{m}}^{\text{–}2}$, with mobility μ $\sim 450\mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{\text{–}1}{\mathrm{s}}^{\text{–}1}$ at low temperatures.

• Received 26 June 2020
• Revised 4 October 2020
• Accepted 29 October 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.4.113404