My research seeks to understand how new quantum phenomena can emerge from the topology of electronic wavefunctions or correlations arising from electron-electron interactions. My group specializes in the development and application of atomic-scale microscopy and spectroscopy to visualize and characterize the nature of such correlated and topological quantum states with high spatial and energy resolution. Our studies have provided unique atomic-resolution data that has enabled validation or constraint of theoretical models for a variety of topological and correlated phenomena in materials.
For instance, in the study of topological phases, emergent Majorana fermions – particles proposed by Ettore Majorana in 1937, that have the unusual property of being its own antiparticle – are predicted to localize at the edge of a topological superconductor, a state of matter that can form when a ferromagnetic system is placed in proximity to a conventional superconductor with strong spin-orbit interaction. In 2014, my group demonstrated how topological superconductivity and Majorana zero modes (MZMs) emerge in chains of ferromagnetic iron atoms on the surface of a superconducting lead. Our group and collaborators developed specialized instrumentation to enable the application of high-resolution spectroscopic mapping with the scanning tunneling microscope (STM) to directly visualize MZMs as the edge-mode excitation of a one-dimensional topological superconductor. Furthermore, we were able to exploit novel spectroscopic techniques with superconducting and spin-polarized STM tips to unequivocally distinguish MZMs from trivial low-energy excitations that may occur in superconductors. Most recently, my group has been working on developing novel atomic-scale imaging instrumentation to explore correlated, superconducting and topological insulating phases in two-dimensional van der Waals materials.
Emergent Phenomena in Quantum Systems