Uncovering and Tuning Correlated Quantum Phases in ABC Graphite on the local scale

The second quantum revolution targets applications in quantum computation, cryptography, and sensing. Materials with strongly correlated quantum phenomena as unconventional superconductivity, fractional charge or topologically protected states are promising candidates. In searching for materials with robust and controllable correlated phases, rhombohedral graphite (RG) stands out due to its particularly simple crystal structure. It is readily available, exceptionally disorder-free, tunable and integrable into manufacturing processes. RG consists of individual graphene layers stacked in the metastable, but robust ABC order that naturally leads to a correlated surface state. Indeed, multiple peculiar quantum states have been found in RG, e.g. the fractional quantum anomalous Hall-effect or various unconventional superconducting phases. However, the state-of-the-art samples are limited to thicknesses of 5 graphene layers. This is detrimental, since the electronic density of the correlated flat band increases with layer thickness promising more robust and distinct phases in thicker samples. The Researcher has recently developed methods to reliably fabricate and identify large, perfectly ABC-stacked graphite flakes up to 12 layers. In this project, we will uncover and tune correlated quantum phases in the largely unexplored thickness range of 6-12 layers. The project combines the singular expertise of the Researcher in sample preparation with the one-of-a-kind equipment of the Host. The scanning tunneling microscopy (STM) technique enables the direct mapping, thus visualizing the correlated electronic phases (magnetic or superconducting states, and perhaps fractional quantum anomalous Hall phases) at the atomic scale. This will facilitate the understanding of new quantum phases of matter. Moreover, the targeted electric switching between different correlated electronic states will potentially enable novel applications using RG, e.g. for topological quantum computing.