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广东快乐十分有计划吗:Strain-induced spontaneous Hall effect in an epitaxial thin film of a Luttinger semimetal
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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, , 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 in 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.
Pyrochlore iridates have provided a plethora of novel phenomena owing to the combination of topology and correlation. Among them, much attention has been paid to , as it is known as a Luttinger semimetal characterized by quadratic band touching at the Brillouin zone center, suggesting that the topology of its electronic states can be tuned by a moderate lattice strain and external magnetic field. Here, we report that our epitaxial thin films grown by solid-state epitaxy exhibit a spontaneous Hall effect that persists up to 50 K without having spontaneous magnetization within our experimental accuracy. This indicates that the system breaks the time reversal symmetry at a temperature scale that is too high for the magnetism to be due to Pr 4f moments and must be related to magnetic order of the iridium 5d electrons. Moreover, our analysis finds that the chiral anomaly induces the negative contribution to the magnetoresistance only when a magnetic field and the electric current are parallel to each other. Our results indicate that the strained part of the thin film forms a magnetic Weyl semimetal state.
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Author contributions: T.O., M.L., and S.N. designed research; T.O., Z.T., A.E., M.H., M.L., and S.N. performed research; T.O., S.K., Y.K., K.K., and M.L. contributed new reagents/analytic tools; T.O., M.L., and S.N. analyzed data; and T.O., M.L., and S.N. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1819489116/-/DCSupplemental.
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