Quadratic Fermi Node in a 3D Strongly Correlated Semimetal

TL;DR

This paper reports the discovery of a quadratic Fermi node in the strongly correlated semimetal Pr2Ir2O7, revealing non-Fermi liquid behavior and potential for various topological phases due to strong spin-orbit and electron-electron interactions.

Contribution

It identifies a nontrivial Fermi node in Pr2Ir2O7, combining experimental and theoretical methods, advancing understanding of correlated topological states in 5d transition metal oxides.

Findings

Identification of a single point Fermi node in Pr2Ir2O7

Evidence of non-Fermi liquid behavior

Potential to realize various topological phases

Abstract

Strong spin-orbit coupling fosters exotic electronic states such as topological insulators and superconductors, but the combination of strong spin-orbit and strong electron-electron interactions is just beginning to be understood. Central to this emerging area are the 5d transition metal iridium oxides. Here, in the pyrochlore iridate Pr2Ir2O7, we identify a nontrivial state with a single point Fermi node protected by cubic and time-reversal symmetries, using a combination of angle-resolved photoemission spectroscopy and first principles calculations. Owing to its quadratic dispersion, the unique coincidence of four degenerate states at the Fermi energy, and strong Coulomb interactions, non-Fermi liquid behavior is predicted, for which we observe some evidence. Our discovery implies that Pr2Ir2O7 is a parent state that can be manipulated to produce other strongly correlated topological phases, such as topological Mott insulator, Weyl semi-metal, and quantum spin and anomalous Hall states.