Anisotropy of the Superconducting State in Sr2RuO4

TL;DR

This study uses small-angle neutron scattering to measure the intrinsic superconducting anisotropy in Sr2RuO4, revealing a much higher anisotropy than previously known, which constrains models of its triplet pairing state.

Contribution

First direct measurement of intrinsic superconducting anisotropy in Sr2RuO4 using neutron scattering, providing new constraints on its pairing symmetry models.

Findings

Intrinsic anisotropy ~60, exceeding upper critical field anisotropy (~20).

Results challenge existing triplet pairing models.

Raises questions about the zero spin projection axis direction.

Abstract

Despite intense studies the exact nature of the order parameter in superconducting Sr2RuO4 remains unresolved. We have used small-angle neutron scattering to study the vortex lattice in Sr2RuO4 with the field applied close to the basal plane, taking advantage of the transverse magnetization. We measured the intrinsic superconducting anisotropy between the c axis and the Ru-O basal plane (~60), which greatly exceeds the upper critical field anisotropy (~20). Our result imposes significant constraints on possible models of triplet pairing in Sr2RuO4 and raises questions concerning the direction of the zero spin projection axis.