Thirty years of puzzling superconductivity in Sr2RuO4

Superconductivity in Sr2RuO4 was discovered 30 years ago. Among the many intriguing aspects of this unconventional superconductor is the picture of spin-triplet superconductivity, which could potentially carry both charge and spin supercurrents. This proposal was considered for a long time but was ultimately disproven in 2019. Despite intense research over the past several years, the superconducting symmetry of the archetypal unconventional superconductor Sr2RuO4 remains unresolved. Here we highlight the recent controversies and give a perspective of how the final resolution may be reached. After 30 years of extensive research, the nature of the unconventional superconductivity in Sr2RuO4 is still not fully understood. This Perspective summarizes the controversies surrounding this and discusses future research.