Multiple superconducting phases of Sr2RuO4

A number of key experiments have provided strong evidence for spin-triplet symmetry in the superconductivity of Sr2RuO4 with T-c = 1.5 K. However, there still remain important issues to be clarified before its superconducting state is fully understood. We will focus on two important issues, which appear to be intimately related to each other. First, we present evidence for multiple superconducting phases of Sr2RuO4 in magnetic fields precisely parallel to the RuO2 plane. Second, we show indications that the upper critical field H-c2 is strongly suppressed when the magnetic field is precisely parallel to the RuO2 plane. We discuss the relationship between these two phenomena, which are both characteristic of the parallel field configuration. (C) 2002 Elsevier Science Ltd. All rights reserved.