The Inner Phases of Colloidal Hexagonal Ice

TL;DR

This paper uses numerical simulations to reveal a novel sequence of phase transitions in colloidal hexagonal ice, including a disordered ice-regime, a charge-ordered state, and a ferromagnetic order, differing from magnetic kagome spin ice.

Contribution

It uncovers a previously unobserved inner phase sequence in colloidal hexagonal ice, highlighting differences from magnetic kagome spin ice due to energetics and frustration.

Findings

Identification of a disordered ice-regime at intermediate repulsion

Discovery of a topologically charge ordered state

Observation of a three-fold degenerate ferromagnetic phase

Abstract

Using numerical simulations that mimic recent experiments on hexagonal colloidal ice, we show that colloidal hexagonal artificial spin ice exhibits an inner phase within its ice state that has not been observed previously. Under increasing colloid-colloid repulsion, the initially paramagnetic system crosses into a disordered ice-regime, then forms a topologically charge ordered state with disordered colloids, and finally reaches a three-fold degenerate, ordered ferromagnetic state. This is reminiscent of, yet distinct from, the inner phases of the magnetic kagome spin ice analog. The difference in the inner phases of the two systems is explained by their difference in energetics and frustration.