Dirac node engineering and flat bands in doped Dirac materials

TL;DR

This paper demonstrates that impurity band engineering in doped Dirac materials can create flat bands and new Dirac nodes, with implications for topological and correlated phases, supported by tight-binding and effective models.

Contribution

It introduces a robust method of impurity band engineering to generate flat bands and additional Dirac nodes in doped Dirac materials, supported by theoretical models.

Findings

Impurity surface states produce nearly flat bands near the Dirac point.

Hybridization causes splitting of Dirac nodes and emergence of new nodes.

Correlation effects preserve flatness of hybridized bands.

Abstract

We suggest the tried approach of impurity band engineering to produce flat bands and additional nodes in Dirac materials. We show that surface impurities give rise to nearly flat impurity bands close to the Dirac point. The hybridization of the Dirac nodal state induces the splitting of the surface Dirac nodes and the appearance of new nodes at high-symmetry points of the Brillouin zone. The results are robust and not model dependent: the tight-binding calculations are supported by a low-energy effective model of a topological insulator surface state hybridized with an impurity band. Finally, we address the effects of electron-electron interactions between localized electrons on the impurity site. We confirm that the correlation effects, while producing band hybridization and Kondo effect, keep the hybridized band flat. Our findings open up prospects for impurity band engineering of nodal structures and flat-band correlated phases in doped Dirac materials.