Whether an actual Mott insulator phase exists in iron pnictides remains elusive. Here, Songet al. demonstrate an antiferromagnetic insulator phase persisting above the Néel temperature in NaFe1−xCuxAs, indicative of a Mott insulator, highlighting the role of electron correlations in high-Tcsuperconductivity.
- Yu Song
- Zahra Yamani
- Pengcheng Dai