Anomalous magnetic noise in imperfect flat bands in the topological magnet Dy2Ti2O7

Understand

The spin ice compound Dy_2Ti_2O_7 stands out as the first topological magnet in three dimensions, with its tell-tale emergent fractionalized magnetic monopole excitations.

• Its real-time dynamical properties have been an enigma from the very beginning.
• Using ultrasensitive, non-invasive SQUID measurements, we show that Dy_2Ti_2O_7 exhibits a highly anomalous noise spectrum, in three qualitatively different regimes: equilibrium spin ice, a `frozen' regime extending to ultra-low temperatures, as well as a high-temperature `anomalous' paramagnet.
• We show that in the simplest model of spin ice, the dynamics is not anomalous, and we present several distinct mechanisms which give rise to a coloured noise spectrum.