The electronic structure of a doped Mott-Hubbard surface

TL;DR

This study combines experimental ARPES, STM, and theoretical models to analyze how boron doping induces metallization and potential superconductivity in a 2D Mott insulator surface, revealing complex electronic structure changes.

Contribution

It provides a comprehensive comparison of experimental data with various electronic structure theories, proposing that sub-subsurface boron doping causes surface metallization.

Findings

Metallization linked to sub-subsurface boron doping

No single theoretical model explains all observations

Surface remains insulating without additional doping layers

Abstract

The Sn/Si(111)-({\sqrt}3{\times}{\sqrt}3)R30{\deg} surface, a 2D Mott insulator, has long been predicted and then found experimetally to metallize and even turn superconducting upon boron doping. In order to clarify the structural, spectroscopic and theoretical details of that evolution, here we present ARPES data supplementing morphology and scanning tunneling measurements. These combined experimental results are compared with predictions from a variety of electronic structure approaches, mostly density functional DFT+U, but not neglecting Mott-Hubbard models, both ordered and disordered. These theoretical pictures address different spectroscopic aspects, including the 2D Fermi surface, the Hubbard bands, etc. While no single picture account for all observations at once,the emergent hypothesis compatible with all data is that metallization arises from sub-subsurface boron doping, additional to the main standard subsurface boron geometry, that would leave the surface insulating. These results advance the indispensable frame for the further understanding of this fascinating system.