Direct observation of the Dirac nodes lifting in semimetallic perovskite SrIrO3 thin films

TL;DR

This study provides direct experimental evidence of the semimetallic electronic structure in SrIrO3 thin films, revealing the lifting of Dirac degeneracy and offering insights into its topological properties and theoretical models.

Contribution

First direct observation of Dirac node lifting in SrIrO3 thin films, challenging existing theories on its topological features and electronic structure.

Findings

Confirmed semimetallic ground state with hole and electron bands crossing Fermi level

Discovered extremely small bandwidth of states near Fermi level

Observed lifting of Dirac degeneracy previously predicted by theory

Abstract

Perovskite SrIrO3 has long been proposed as an exotic semimetal induced by the interplay between the spin-orbit coupling and electron correlations. However, its low-lying electronic structure is still lacking. We synthesize high-quality perovskite SrIrO3 (100) films by means of oxide molecular beam epitaxy, and then systemically investigate their low energy electronic structure using in-situ angle-resolved photoemission spectroscopy. We find that the hole-like bands around R and the electron-like bands around U(T) intersect the Fermi level simultaneously, providing the direct evidence of the semimetallic ground state in this compound. Comparing with the density functional theory, we discover that the bandwidth of states near Fermi level is extremely small, and there exists a pronounced mixing between the Jeff = 1/2 and Jeff = 3/2 states. Moreover, our data reveal that the predicted Dirac degeneracy protected by the mirror-symmetry, which was theoretically suggested to be the key to realize the non-trivial topological properties, is actually lifted in perovskite SrIrO3 thin films. Our findings pose strong constraints on the current theoretical models for the 5d iridates.