Strain-induced spontaneous Hall effect in an epitaxial thin film of a Luttinger semimetal

Significance Weyl semimetals carry the promise of quantum electronic applications. Theoretical calculations have suggested that Luttinger semimetals recently found in iridium oxides may be a suitable group of materials where such topological phases, including Weyl semimetal state, may be found. For example, praseodymium-iridium oxide,P r 2 I r 2 O 7 , is one such Luttinger semimetal that can be tuned by perturbations such as strain into a Weyl semimetal state. Despite theoretical predictions of Weyl semimetal states inP r 2 I r 2 O 7 crystals, experimental proof remains elusive due to the difficulty of applying sufficient mechanical strain on single crystals. Our study provides strong experimental evidence that a Weyl semimetal state may indeed appear in strained pyrochlore iridium oxide films, opening a way to explore topological phases.