A doped Mott insulator’s behaviour lies at the heart of some of the most exotic physical phenomena in materials research. The adsorption of a one-third monolayer of Sn atoms on a Si(111) surface produces a triangular surface lattice with half-filled dangling bond orbitals. In this talk, I will show how modulation hole doping of these dangling bonds unveils clear hallmarks of Mott physics [1], including a spectral weight transfer and the formation of dispersive quasiparticles at the Fermi level. I will also discuss the recent observation of superconductivity [2] in the most heavily hole-doped monolayers and evidence for an unconventional d+id chiral order parameter obtained from quasiparticle interference imaging and state-of-the-art calculations in the dynamical cluster approximation. These observations are remarkably similar to those made in complex oxide materials, including high-temperature superconductors, but highly extraordinary within the realm of conventional sp-bonded semiconductor materials. 

References:

[1] F. Ming et al., PRL 119, 266802 (2017).

[2] X. Wu et al., PRL 125, 117001 (2020).