Evidence for strong electron correlations in a non-symmorphic Dirac semimetal

TL;DR

This study provides evidence of strong electron correlations and topological features in monoclinic SrIrO₃, a non-symmorphic Dirac semimetal, through quantum oscillations, theoretical calculations, and transport measurements.

Contribution

It reports the first observation of quantum oscillations in high-quality SrIrO₃ crystals and links these to non-symmorphic symmetry and strong electron correlations.

Findings

Multiple small Fermi surface pockets with heavy effective masses

Presence of linear band crossings due to non-symmorphic symmetry

Signatures of non-Fermi liquid behavior and high Kadowaki-Woods ratio

Abstract

Metallic iridium oxides (iridates) provide a fertile playground to explore new phenomena resulting from the interplay between topological protection, spin-orbit and electron-electron interactions. To date, however, few studies of the low energy electronic excitations exist due to the difficulty in synthesising crystals with sufficiently large carrier mean-free-paths. Here, we report the observation of Shubnikov-de Haas quantum oscillations in high-quality single crystals of monoclinic SrIrO$_3$ in magnetic fields up to 35~T. Analysis of the oscillations reveals a Fermi surface comprising multiple small pockets with effective masses up to 4.5 times larger than the calculated band mass. \textit{Ab-initio} calculations reveal robust linear band-crossings at the Brillouin zone boundary, due to its non-symmorphic symmetry, and overall we find good agreement between the angular dependence of the oscillations and the theoretical expectations. Further evidence of strong electron correlations is realized through the observation of signatures of non-Fermi liquid transport as well as a large Kadowaki-Woods ratio. These collective findings, coupled with knowledge of the evolution of the electronic state across the Ruddlesden-Popper iridate series, establishes monoclinic SrIrO$_3$ as a topological semimetal on the boundary of the Mott metal-insulator transition.