SmO thin films: a flexible route to correlated flat bands with nontrivial topology

TL;DR

This paper predicts that SmO thin films are a promising platform for exploring topologically nontrivial correlated flat bands, with robust surface states and tunable properties via strain, based on density functional theory calculations.

Contribution

It demonstrates that SmO is a robust 3D topological semi-metal with potential for thin-film applications and novel quantum phenomena, highlighting its unique band inversion and interface possibilities.

Findings

SmO exhibits a 4f-5d band inversion at the X point.

Surface spectral density shows Dirac cones at specific points.

Topological properties are stable over a range of lattice parameters.

Abstract

Using density functional theory based calculations, we show that the correlated mixed-valent compound SmO is a 3D strongly topological semi-metal as a result of a 4$f$-5$d$ band inversion at the X point. The [001] surface Bloch spectral density reveals two weakly interacting Dirac cones that are quasi-degenerate at the M_bar-point and another single Dirac cone at the Gamma_bar-point. We also show that the topological non-triviality in SmO is very robust and prevails for a wide range of lattice parameters, making it an ideal candidate to investigate topological nontrivial correlated flat bands in thin-film form. Moreover, the electron filling is tunable by strain. In addition, we find conditions for which the inversion is of the 4f-6s type, making SmO to be a rather unique system. The similarities of the crystal symmetry and the lattice constant of SmO to the well studied ferromagnetic semiconductor EuO, makes SmO/EuO thin film interfaces an excellent contender towards realizing the quantum anomalous Hall effect in a strongly correlated electron system.