Orbital-singlet pairing and order parameter symmetry in Sr_2RuO_4

TL;DR

This paper proposes that in Sr_2RuO_4, Cooper pairs form orbital singlets with spin-triplet pairing, leading to an A_{1g} symmetric order parameter consistent with experimental data and explaining impurity sensitivity.

Contribution

It introduces the concept of orbital singlet pairing in Sr_2RuO_4 and demonstrates its compatibility with observed experimental properties.

Findings

Order parameter has A_{1g} symmetry.

Orbital singlet pairing explains impurity sensitivity.

Consistent with multiple experimental observations.

Abstract

Based on the degeneracy of the d_{zx} and d_{yz} orbitals in Sr_2RuO_4 it is argued that the Cooper pairs condense in orbital singlets. Together with the spin-triplet wave functions the real-space wave function then is symmetric. Considering interaction effects the order parameter is found to have A_{1g} symmetry consistent with a number of experimental observations. The sensitivity of the material on non-magnetic impurities follows in a straightforward manner from the orbital-singlet configuration.