Recreating the Physics of a Doped Mott Insulator on a Silicon Surface

Sn adatoms on a Si(111) substrate with 1/3 monolayer coverage form a two-dimensional triangular lattice with one unpaired electron per site and an antiferromagnetic Mott insulating state. The Sn layers can be modulation hole-doped and metalized using heavily-doped p-type Si(111) substrates and become superconducting at low temperatures, recreating cuprate-like physics on a Si template. Here, the combination of repulsive interactions and frustration inherent to the triangular adatom lattice opens up the possibility for a chiral order parameter. In this talk, I will discuss recent theoretical and experimental studies leveraging scanning tunneling microscopy/spectroscopy and quasi-particle interference imaging to study this novel system. We find evidence for a doping-dependent Tc with a fully gapped order parameter, time-reversal symmetry breaking, and a substantial enhancement of the zero-bias conductance near the edges of the superconducting domains. While each piece of evidence could have a more mundane interpretation, our combined results suggest the tantalizing possibility that Sn/Si(111) is an unconventional chiral d-wave superconductor, consistent with theoretical models.<br/><br/>References<br/>1) F. Ming et al., Physical Review Letters 119, 266802 (2017).<br/>2) X. Wu et al., Physical Review Letters 125, 117001 (2020).<br/>3) F. Ming et al., Nature Physics 19, 500–506 (2023).