  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.
