Universal Dynamics of Magnetic Monopoles in Two-Dimensional Kagomé Ice

A magnetic monopole in spin ice is a novel quasiparticle excitation in condensed matter physics. We found that the ac frequency dependent magnetic susceptibility χ(ω) in the two-dimensional (2D) spin ice (so-called kagomé ice) of Dy2Ti2O7 shows a single scaling form. This behavior can be understood in terms of the dynamical scaling law for 2D Coulomb gas (CG) systems [Phys. Rev. B 90, 144428 (2014)], characterized by the charge correlation length ξ (∝1/√ω1), where ω1 is a characteristic frequency proportional to the peak position of the imaginary part of χ(ω). It is a generic behavior among a wide variety of models such as the vortex dynamics of 2D superconductors, 2D superfluids, classical XY magnets, and dynamics of melting of Wigner crystals.