Incommensurability in the Frustrated Two-Dimensional XY Model

To examine the properties of the frustrated XY model at an incommensurate field we have examined a sequence of magnetic filling factors f which approach the irrational value of one minus the golden mean. At all f studied, the system undergoes a finite-temperature weak first-order transition involving the freezing out of Ising-like domain walls. As one approaches incommensurability, the low temperature phase of the system changes from the staircase states found by Halsey to a striped phase consisting of a superlattice of parallel shift (Pott's-like) domain walls.