Monoclinic SrIrO3—a Dirac semimetal produced by non-symmorphic symmetry and spin–orbit coupling

T Takayama,A N Yaresko,H Takagi

doi:10.1088/1361-648x/aaf68a

Abstract

SrIrO3 crystallizes in a monoclinic structure of distorted hexagonal perovskite at ambient pressure. The transport measurements show that the monoclinic SrIrO3 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.

Highlights

The transport measurements show that the monoclinic SrIrO3 is a low-carrier density semimetal, as in the orthorhombic perovskite polymorph
We note that χ0 − χcore should include χP and van Vleck contribution χVV, which can be as large as ∼ 10−4 emu/mol in iridates [19]. If it is the case, the Wilson ratio RW is very close to 1 rather than the nave estimate using χ0 − χcore. This gives a reasonable doubt on the enhanced RW in the monoclinic SrIrO3
We found that the monoclinic SrIrO3 is a semimetal from the transport measurements

Summary

Introduction

5d transition-metal oxides recently emerged as a platform for the exploration of novel electronic states produced by the interplay of modest Coulomb interaction U with strong spin-orbit coupling λSO [1]. The strong spin-orbit coupling of Ir as large as 0.5 eV splits the t2g manifold into the lower-lying fully-filled Jeff = 3/2 quartet and the upper Jeff = 1/2 doublet with one electron (hole), forming a half-filled band of predominant Jeff = 1/2 character [2]. The spin-orbital entangled character of Jeff = 1/2 wave function gives rise to bond-sensitive exchange coupling and the resultant unconventional magnetic ground states, as demonstrated by the twodimensional Heisenberg antiferromagnetism in the layered perovskite Sr2IrO4 [4] and the Kitaev magnetism in honeycomb-based iridates [5]. One may naively expect that all of the Jeff = 1/2 metals have a large Fermi surface originating from the half-filled Jeff = 1/2 bands These metallic iridates, were very often found to be a semimetal [8, 9], which is discussed to be a consequence of the interplay of strong spin-orbit coupling and the lattice distortion. The Ir(1)Ir(2)O9 bilayers consisting of the Ir(1)O6 layer and one Ir(2)O6 layer connected by the corner oxygens may be viewed as a buckled honeycomb structure as in the (111) superlattice of cubic perovskite [15]

Results

Discussion

Conclusion