Nematicity of a Magnetic Helix

TL;DR

This paper introduces a new magnetic nematic phase based on magnetic helices, characterized using soft X-ray scattering, revealing two distinct phases with unique correlations and dynamic fluctuations near phase boundaries.

Contribution

The study presents the first experimental realization and detailed characterization of a magnetic nematic phase using a helical basis and advanced X-ray techniques.

Findings

Discovery of two distinct magnetic nematic phases.

Observation of coexisting fluctuations on multiple timescales.

Identification of spontaneous symmetry breaking during phase transition.

Abstract

A system that possesses translational symmetry but breaks orientational symmetry is known as a nematic phase. While there are many examples of nematic phases in a wide range of contexts, such as in liquid crystals, complex oxides, and superconductors, of particular interest is the magnetic analogue, where the spin, charge, and orbital degrees of freedom of the electron are intertwined. The difficulty of spin nematics is the unambiguous realization and characterization of the phase. Here we present an entirely new type of magnetic nematic phase, which replaces the basis of individual spins with magnetic helices. The helical basis allows for the direct measurement of the order parameters with soft X-ray scattering and a thorough characterization of the nematic phase and its thermodynamic transitions. We discover two distinct nematic phases with unique spatio-temporal correlation signatures. Using coherent X-ray methods, we find that near the phase boundary between the two nematic phases, fluctuations coexist on the timescale of both seconds and sub-nanoseconds. Additionally, we have determined that the fluctuations occur simultaneously with a reorientation of the magnetic helices, indicating that there is spontaneous symmetry breaking and new degrees of freedom become available. Our results provide a novel framework for characterizing exotic phases and the phenomena presented can be mapped onto a broad class of physical systems.