Thickness-dependent quantum transport of Weyl fermions in ultra-high-quality SrRuO3 films

TL;DR

This study investigates how the quantum transport properties of Weyl fermions in SrRuO3 films depend on thickness, revealing conditions for observing Weyl fermion signatures in ultra-high-quality epitaxial films.

Contribution

It demonstrates the thickness-dependent magnetotransport behavior of Weyl fermions in SrRuO3 films and identifies the residual resistivity ratio threshold for their observation.

Findings

Weyl fermion transport signatures observed in films as thin as 10 nm.

Residual resistivity increases with decreasing film thickness.

Threshold residual resistivity ratio for Weyl fermion transport is 21.

Abstract

The recent observation of Weyl fermions in the itinerant 4d ferromagnetic perovskite SrRuO3 points to this material being a good platform for exploring novel physics related to a pair of Weyl nodes in epitaxial heterostructures. In this letter, we report the thickness-dependent magnetotransport properties of ultra-high-quality epitaxial SrRuO3 films grown under optimized conditions on SrTiO3 substrates. Signatures of Weyl fermion transport, i.e., unsaturated linear positive magnetoresistance accompanied by a quantum oscillation having a {\pi} Berry phase, were observed in films with thicknesses as small as 10 nm. Residual resistivity increased with decreasing film thickness, indicating disorder near the interface between SrRuO3 and the SrTiO3 substrate. Since this disorder affects the magnetic and electrical properties of the films, the Curie temperature decreases and the coercive field increases with decreasing thickness. Thickness-dependent magnetotransport measurements revealed that the threshold residual resistivity ratio (RRR) to observe Weyl fermion transport is 21. These results provide guidelines for realizing quantum transport of Weyl fermions in SrRuO3 near heterointerfaces.