Strong peak in T c of Sr ₂ RuO ₄ under uniaxial pressure

Squeezing out the oddness The material Sr 2 RuO 4 has long been thought to exhibit an exotic, odd-parity kind of superconductivity, not unlike the superfluidity in 3 He. How would perturbing this material's electronic structure affect its superconductivity? Steppke et al. put the material under large uniaxial pressure and found that the critical temperature more than doubled and then fell as a function of strain (see the Perspective by Shen). The maximum critical temperature roughly coincided with the point at which the material's Fermi surface underwent a topological change. One intriguing possibility is that squeezing changed the parity of the superconducting gap from odd to even. Science , this issue p. 10.1126/science.aaf9398 ; see also p. 133