Researchers are increasingly focused on understanding the complex behaviour of correlated multi-orbital systems, and a new study details how geometric frustration impacts electronic properties in a specific nickelate material. Yidian Li, Mingxin Zhang from ShanghaiTech University, and Xian Du, alongside Cuiying Pei, Jieyi Liu, and Houke Chen et al., present compelling evidence of orbital-selective Mottness in Pr4Ni3O10, revealing a striking contrast with La4Ni3O10. Their work, utilising high-resolution angle-resolved photoemission spectroscopy and theoretical modelling, demonstrates that subtle changes in the interlayer Ni-O-Ni bonding angle can significantly modulate the coherence of electron orbitals. This finding is significant because it identifies a structural…