Investigating Mobility and Entropy in 2D Magnetic Monopole Gas Systems

The two-dimensional monopole gas (2DMG) is a novel system arising at the interface between a frustrated spin ice and an antiferromagnet, resulting in a non-zero net magnetic charge of the monopole quasiparticles. While the behavior of spin ice is well understood, 2DMG introduces a new degree of freedom for magnetic charge with charged monopoles that remain largely unexplored. In this study, we demonstrate that the monopoles contribute entropy and have unique mobility characteristics. Using comprehensive Monte Carlo simulations of an R2Ir2O7/R2Ti2O7/R2Ir2O7 heterostructure we explored these properties across a large range of applied electric fields, temperatures, and heterostructure geometry, yielding data on conductivity, mobility, and entropy. The simulations revealed a pronounced Hall effect at low temperatures, signaling increased monopole mobility as the temperature decreased. Additionally, the system's entropy exhibited a non-linear dependence on layer thickness, which we attribute to the influence of monopoles. Our results reveal significant contributions of monopoles to the entropy of the spin ice and a pronounced Hall effect, which can serve as a probe to determine the magnetic charge of the 2DMG. These findings enhance the understanding of monopole dynamics and provide insights for engineering 2DMG systems.