Monoclinic SrIrO$_3$ - A Dirac semimetal produced by non-symmorphic symmetry and spin-orbit coupling

TL;DR

This paper reports that monoclinic SrIrO₃ is a Dirac semimetal whose Dirac bands are protected by non-symmorphic symmetry and strong spin-orbit coupling, revealing a novel topological state in this material.

Contribution

It demonstrates that the Dirac semimetallic state in monoclinic SrIrO₃ arises from non-symmorphic symmetry combined with spin-orbit coupling, a novel mechanism for topological semimetals.

Findings

SrIrO₃ is a low-carrier density semimetal.

Dirac bands appear at high-symmetry points with spin-orbit coupling.

Dirac bands are protected by non-symmorphic symmetry.

Abstract

SrIrO$_3$ crystallizes in a monoclinic structure of distorted hexagonal perovskite at ambient pressure. The transport measurements show that the monoclinic SrIrO$_3$ is a low-carrier density semimetal, as in the orthorhombic perovskite polymorph. The electronic structure calculation indicates a semimetallic band structure with Dirac bands at two high-symmetry points of Brillouin zone only when spin-orbit coupling is incorporated, suggesting that the semimetallic state is produced by the strong spin-orbit coupling. We argue that the Dirac bands are protected by the non-symmorphic symmetry of lattice.