| Even though less studied than their hole-doped counterparts, the understanding of the electron-doped cuprates is essential for a universal picture of high-temperature superconductivity. In order to reach this goal, it is crucial to solve the main mystery that holds since the discovery of these materials: why is superconductivity achieved only when a tiny amount of oxygen is removed in the as-grown samples during a post-annealing process (reduction)? To solve this issue, we have performed a systematic ARPES study of as-grown and reduced samples. We show that the main impact of the reduction process is to suppress long-range antiferromagnetism, thus ungapping the nodal region of the Fermi surface. |
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