Strongly correlated iridate pyrochlores with geometrically frustrated spins have been recognized as a potentially interesting group of oxide materials where novel topological phases may appear. A particularly attractive system is the metallic Pr2Ir2O7, as it is known as a Fermi node semimetal characterized by quadratic band touching at the Brillouin zone center, suggesting that the topology of its electronic states can be tuned by moderate lattice strain. In this work we report the growth of epitaxial Pr2Ir2O7 thin films grown by solid-state epitaxy. We show that the strained parts of the films give rise to a spontaneous Hall effect that persists up to 50 K without having spontaneous magnetization within our experimental accuracy. This indicates that a macroscopic time reversal symmetry (TRS) breaking appears at a temperature scale that is too high for the magnetism to be due to Pr 4f moments, and must thus be related to magnetic order of the iridium 5d electrons. The magnetotransport and Hall analysis results are consistent with the formation of a Weyl semimetal state that is induced by a combination of TRS breaking and cubic symmetry breaking due to lattice strain.
@article{arxiv.1711.07813,
title = {Spontaneous Hall effect induced by strain in Pr$_2$Ir$_2$O$_7$ epitaxial thin films},
author = {Takumi Ohtsuki and Zhaoming Tian and Akira Endo and Mario Halim and Shingo Katsumoto and Yoshimitsu Kohama and Koichi Kindo and Satoru Nakatsuji and Mikk Lippmaa},
journal= {arXiv preprint arXiv:1711.07813},
year = {2017}
}