Dynamical fractal and anomalous noise in a clean magnetic crystal

HALLÉN, JONATHAN N.; GRIGERA, SANTIAGO A.; TENNANT, D. ALAN; CASTELNOVO, CLAUDIO; MOESSNER, RODERICH

SCIENCE

AMER ASSOC ADVANCEMENT SCIENCE

Año: 2022 vol. 378 p. 1218 - 1221

0036-8075

Fractals—objects with noninteger dimensions—occur in manifold settings and length scales innature. In this work, we identify an emergent dynamical fractal in a disorder-free, stoichiometric, andthree-dimensional magnetic crystal in thermodynamic equilibrium. The phenomenon is born fromconstraints on the dynamics of the magnetic monopole excitations in spin ice, which restrict them tomove on the fractal. This observation explains the anomalous exponent found in magnetic noiseexperiments in the spin ice compound Dy 2 Ti 2 O 7 , and it resolves a long-standing puzzle about itsrapidly diverging relaxation time. The capacity of spin ice to exhibit such notable phenomenasuggests that there will be further unexpected discoveries in the cooperative dynamics of evensimple topological many-body systems