# Vortex lattices and broken time reversal symmetry in the topological superconductor UPt3

## TL;DR

This study investigates vortex lattice configurations in the topological superconductor UPt3, revealing broken time reversal symmetry and chiral order, with field-dependent vortex behavior indicating unconventional superconductivity.

## Contribution

It provides direct experimental evidence of vortex lattice asymmetry and non-monotonic rotation in UPt3, demonstrating broken time reversal symmetry and internal vortex degrees of freedom.

## Key findings

- Vortex lattice configuration depends on magnetic field sign.
- Discovery of field-driven non-monotonic vortex lattice rotation.
- Evidence of broken time reversal symmetry in UPt3 B phase.

## Abstract

The topological superconductor UPt3, has three distinct vortex phases, a strong indication of its unconventional character. Using small-angle neutron scattering we have probed the vortex lattice in the UPt3 B phase with the magnetic field along the crystal c-axis. We find a difference in the vortex lattice configuration depending on the sign of the magnetic field relative to the field direction established upon entering the B phase at low temperature in a field sweep, showing that the vortices in this material posses an internal degree of freedom. This observation is facilitated by the discovery of a field driven non-monotonic vortex lattice rotation, driven by competing effects of the superconducting gap distortion and the vortex-core structure. From our bulk measurements we infer that the superconducting order parameter in the UPt3 B phase breaks time reversal symmetry and exhibits chiral symmetry with respect to the c-axis.