Is Sr2RuO4 a triplet superconductor?

Abstract

The field dependence of the specific heat γ(H) at lower temperatures in Sr2RuO4 is analyzed by solving microscopic Eilenberger equation numerically. We find that systematic γ(H) behaviors from a concaved \sqrt H to a convex H^α (α>1) under H orientation change are understood by taking account of the Pauli paramagnetic effect. The magnetizations are shown to be consistent with it. This implies either a singlet pairing or a triplet one with d-vector locked in the basal plane, which allows us to explain other mysteries of this compound in a consistent way.