In addtion to the regular PQM discussion group, this week we will have an additional seminar. It will be delivered by Prof Chris Hooley (Coventry University) on Friday 12 December, 2025, at 10am, in the Howard Rogers Room (Ingram 234), speaking on this topic:
Why doesn’t the surface of the superconductor Sr2RuO4 superconduct?
Sr2RuO4 is a metallic layered perovskite material, originally investigated because of its chemical and structural similarity to La2CuO4, the parent compound of one of the families of cuprate high-temperature superconductors. Quickly, however, the stories diverged, and for a long time it was believed that Sr2RuO4 was a triplet superconductor with p+ip pairing. In the light of new experimental evidence, though, the order parameter symmetry (i.e. the shape of the Cooper pair wave function) seems less certain.
There is another experimental puzzle associated with Sr2RuO4: why (at least typically) is the superconductivity not seen in surface measurements, e.g. scanning tunnelling microscopy (STM)? In this talk, I shall explain our answer to this question; along the way, we will give our assessment of the likely order-parameter symmetry of the bulk superconductivity, and point out a way in which the superconducting critical temperature could be enhanced from its usual value.
Main reference: J. B. Profe, L. C. Rhodes, M. Dürrnagel, R. Bisset, C. A. Marques, S. Chi, T. Schwemmer, R. Thomale, D. M. Kennes, CAH, and P. Wahl, “Magic angle of Sr2RuO4: Optimizing correlation-driven superconductivity,” Phys. Rev. Research 6, 043057 (2024).