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Magnetic pyrochlore iridates are a class of compounds where the competition between spin-orbit coupling and electronic correlation results in intriguing physical properties, such as metal-insulator transition and topological phases. Among them, Eu₂Ir₂O₇ has been predicted to be a Weyl semimetal in its low temperature all-in-all-out magnetic phase; however, the experimental results are controversial. While transport experiments suggest an antiferromagnetic insulator, optical response reveals a Weyl semimetallic electronic structure.
Here, using first principles calculations supported by low fluence pump-probe spectroscopy, we clarify how the low energy electronic structure of Eu₂Ir₂O₇ evolves with the emergence of all-in-all-out magnetic ordering. Our results highlight the role of stoichiometric control towards stabilizing the Weyl semimetal phase in the pyrochlore iridates.