In situ engineering of quantum materials

A major frontier in quantum materials research is the ability not only to observe electronic structure, but also to modify it in a controlled way directly in vacuum. By combining surface-sensitive spectroscopy with in situ tuning methods such as adatom deposition, strain, and interface engineering, it becomes possible to create and manipulate electronic phases that would be inaccessible in bulk materials or unstable outside ultra-high vacuum. This approach opens a powerful route toward designing quantum states of matter while probing their microscopic origin in real time.

Our work has pursued this idea across several material platforms. In an early study of cuprate superconductors, we demonstrated in situ control of the self-doped surface electronic structure arising from the polar catastrophe, establishing a route to tuning YBa₂Cu₃O_6+x directly in vacuum across its full  phase diagram. In graphene, we then used in situ engineering to induce and probe striking new electronic phenomena, including evidence for superconductivity in Li-decorated monolayer graphene, strain-induced pseudo-Landau levels at room temperature, and global density-wave formation with Kekulé order driven by local symmetry breaking. In the topological insulator Bi2​Se3​, we demonstrated control of Rashba spin splitting at the surface, showing how spin-textured electronic states can be tuned directly through surface modification.

More recently, in LaSbTe, we demonstrated reversible electronic switching of topology, showing how quantum states can be actively controlled rather than simply characterized. Together, these studies illustrate our broader effort to move from measuring quantum materials to deliberately engineering their electronic structure and functionality.