Extending spin ice concepts to another geometry: The artificial triangular spin ice

In this work, we propose and study a realization of an artificial spin-ice-like system in a triangular geometry, which, unlike square and kagome artificial spin ice, is not based on any real material. At each vertex of the lattice, the ``icelike rule'' dictates that three spins must point inward while the other three must point outward. We have studied the system's ground state and the lowest energy excitations as well as the thermodynamic properties of the system. Our results show that, despite fundamental differences in the vertex topologies as compared to the artificial square spin ice, in the triangular array the lowest energy excitations also behave like Nambu monopoles (two opposite monopoles connected by an energetic string). Indeed, our results suggest that the charge intensity of the monopoles may have a universal value while the string tension could be tuned by changing the system's geometry, probably allowing the design of systems with different string tensions. Our Monte Carlo findings suggest a phase transition in the Ising universality class where the mean distance between monopoles and antimonopoles increases considerably at the critical temperature. The differences in the vertex topologies seem to facilitate the experimental achievement of the system's ground state, thereby allowing a more detailed experimental study of the system's properties.