Wednesday, August 29, 2012

1208.5765 (F. S. Nascimento et al.)

From confinement to deconfinement of magnetic monopoles in artificial
rectangular spin ices

F. S. Nascimento, L. A. S. Mól, W. A. Moura-Melo, A. R. Pereira
We study a frustrated two-dimensional array of dipoles forming an artificial rectangular spin ice with horizontal and vertical lattice parameters given by $a$ and $b$ respectively. We show that the ice regime could be stabilized by appropriate choices for the ratio $a/b$. Indeed, for special values of $\gamma \equiv a/b$, the ground state becomes degenerate. Therefore, while the magnetic charges (monopoles) are excitations connected by an energetic string for general rectangular lattices (including the particular case of a square lattice), they are free to move for a special rectangular lattice with $a/b\approx 1.735$ or 0.556. We also discuss the ground state transition and some thermodynamic properties of the system.
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