Nanoscale Imaging of a Topological Insulator Grown on a Cuprate Superconductor using Molecular Beam Epitaxy

When an s-wave superconductor (SC) is interfaced with a topological insulator (TI), the TI can become superconducting by proximity. The emergent phase of matter is predicted to host Majorana zero modes (Fu and Kane, PRL 100, 096407 (2008)), and has promising applications in quantum computation. In contrast to a well-understood theoretical framework of s-wave SC/TI heterostructures, it is unclear if Majorana zero modes are expected to appear in a d-wave SC/TI heterostructure. Moreover, the experiments so far have reported conflicting observations of proximity-induced superconductivity in these systems (Wang et al., Nature Physics 9, 621 (2013), Yilmaz et al., PRL 113, 077003 (2014)). To shed light on this, we perform scanning tunneling microscopy/spectroscopy experiments of a prototypical topological insulator Bi₂Te₃ grown on a cuprate high-T_c superconductor Bi₂Sr₂CaCu₂O_8+x using molecular beam epitaxy. We characterize the electronic band structure of the topmost TI surface using quasiparticle interference imaging, and discuss the implications of our measurements on previous observations of proximity-induced superconductivity in this system.