The Colored Noise of Spin Ice: Subdiffusion of Magnetic Monopoles in a Coevolving Vacuum
We relate the anomalous noise found experimentally in spin ice to the subdiffusion of magnetic monopoles. As emergent particles, monopoles do not move in a structureless vacuum. Rather, the underlying spin ensemble filters the thermal white noise. Certain hops are forbidden by by the local spin structure, which in turns is changed by monopole passage, leading to non-trivial coevolution. Thus, monopoles can be considered as random walkers under the effect of stochastic forces, as long as those are endowed with a memory which subsumes the evolution of the non-trivial vacuum. We conjecture relations between the anomalous noise and the exponent of anomalous subdiffusion, the fractal dimension of the walk and the dynamical critical index.