Magnetic field induced rotation of thed-vector in the spin-triplet superconductorSr2RuO4

Abstract

In zero magnetic field the superconductor ${\text{Sr}}_{2}{\text{RuO}}_{4}$ is believed to have a chiral spin-triplet pairing state in which the gap function $d$-vector is aligned along the crystal $c$ axis. Using a phenomenological but orbital specific description of the spin-dependent electron-electron attraction and a realistic quantitative account of the electronic structure in the normal state, we analyze the orientation of the spin-triplet Cooper pair $d$-vector in response to an external $c$-axis magnetic field. We show that, for suitable values of the model parameters, a $c$-axis field of only $20\text{ }\text{mT}$ is able to cause a reorientation phase transition of the $d$-vector from along $c$ to the $a$ plane, in agreement with recent experiments.