Resonant tunneling between Landau levels formed in topological insulator surfaces realized in epitaxially grown van der Waals heterostructures

Tunneling spectroscopy in van der Waals heterostructures with highly crystalline and atomically sharp interfaces provides a powerful tool to probe the density of states of the materials and the selection rule of tunneling electrons. Here, we present the fabrication and electric transport characterization of vertical tunnel junctions made of topological insulators (TIs) separated by an a-few-atom-thick hBN tunnel barrier. We grow Bi₂Se₃ and Sb₂Te₃, which are n– and p–type TIs, respectively, on both sides of suspended ultrathin hBN layers using molecular beam epitaxy. Our high-resolution transmission electron microscopy reveals an atomically abrupt and epitaxial interface between the hBN substrate and the top- and bottom-TIs. We perform field-angle-dependent magneto-tunneling spectroscopy on the junctions and observe energy-momentum-spin resonance of Dirac electrons tunneling between helical Landau levels developed in the topological surface states.