Engineering correlated Dirac fermions and flat bands on SiC with transition-metal adatom lattices

TL;DR

This paper explores transition-metal adatom lattices on SiC surfaces as a platform for realizing Dirac fermions and flat bands, revealing diverse correlated electronic phases through advanced theoretical methods.

Contribution

It introduces a new class of adatom systems on SiC that exhibit tunable Dirac and flat band features with strong correlations, analyzed via density functional theory and many-body techniques.

Findings

Cr forms flat band Fermi liquids

V exhibits paramagnetic Mott insulating behavior

Ti shows proximity to heavy Dirac semimetal phase

Abstract

We propose three transition-metal adatom systems on 3C-SiC(111) surfaces as a versatile platform to realize massless Dirac fermions and flat bands with strong electronic correlations. Using density functional theory combined with the constrained random phase approximation and dynamical mean-field theory, we investigate the electronic properties of Ti, V, and Cr adatoms. The triangular surface lattices exhibit narrow bandwidths and effective two-band Hubbard models near the Fermi level, originating from partially filled, localized d-orbitals of the adatoms. Our study reveals a materials trend from a flat band Fermi liquid (Cr) via a paramagnetic Mott insulator with large local moments (V) to a Mott insulator on the verge to a heavy Dirac semimetal (Ti) showcasing the diverse nature of these strongly correlated systems. Specifically, the flat bands in the Cr and the well-defined Dirac cones in the strained metallic~Ti lattice indicate high potential for realizing topological and correlated phases.