Oxygen vacancy-driven orbital multichannel Kondo effect in Dirac nodal line metals IrO2 and RuO2

TL;DR

This paper reports the experimental observation of orbital one- and two-channel Kondo effects driven by oxygen vacancies in Dirac nodal line metals IrO2 and RuO2 nanowires, revealing new topological quantum states.

Contribution

It demonstrates the emergence of nonmagnetic Kondo correlations in Dirac nodal line metals, a phenomenon previously difficult to observe in real materials.

Findings

Observation of orbital Kondo effects in IrO2 and RuO2 nanowires

Symmetry-enforced Dirac nodal lines promote Kondo correlations

Nanostructures as platforms for topological quantum states

Abstract

Strong electron correlations have long been recognized as driving the emergence of novel phases of matter. A well recognized example is high-temperature superconductivity which cannot be understood in terms of the standard weak-coupling theory. The exotic properties that accompany the formation of the two-channel Kondo effect including the emergence of an unconventional metallic state in the low-energy limit also originate from strong electron interactions. Despite its paradigmatic role for the formation of non-standard metal behavior, the stringent conditions required for its emergence have made the observation of the nonmagnetic, orbital two-channel Kondo effect in real quantum materials difficult, if not impossible. We report the observation of orbital one- and two-channel Kondo physics in the symmetry-enforced Dirac nodal line metals IrO2 and RuO2 nanowires and show that the symmetries that enforce the existence of Dirac nodal lines also promote the formation of nonmagnetic Kondo correlations. Rutile oxide nanostructures thus form a versatile quantum matter platform to engineer and explore intrinsic, interacting topological states of matter.