# Spin Susceptibility of the Topological Superconductor UPt3 from Polarized Neutron Diffraction

## TL;DR

This study uses polarized neutron scattering to measure the bulk spin susceptibility of UPt3, challenging the reliability of Knight shift as an indicator of its topological odd-parity superconducting state.

## Contribution

It provides experimental evidence that questions the use of Knight shift as a definitive marker for odd-parity superconductivity in UPt3.

## Key findings

- Bulk susceptibility aligns with Knight shift measurements
- Results are inconsistent with existing theoretical predictions for this orientation
- Suggests Knight shift may not reliably indicate odd-parity in UPt3

## Abstract

Experiment and theory indicate that UPt3 is a topological superconductor in an odd-parity state, based in part from temperature independence of the NMR Knight shift. However, quasiparticle spin-flip scattering near a surface, where the Knight shift is measured, might be responsible. We use polarized neutron scattering to measure the bulk susceptibility with H||c, finding consistency with the Knight shift but inconsistent with theory for this field orientation. We infer that neither spin susceptibility nor Knight shift are a reliable indication of odd-parity.