Complex Collective Effects in Vertex Frustrated Artificial Spin Ice

Artificial spin ice systems are arrays of lithographically fabricated single-domain ferromagnetic elements with geometrically determined interactions that determine their collective properties. The ability to both design the lattice geometries and probe the individual moments in these systems allows the study of frustration in ways that are unavailable in natural materials. Our group has conducted a range of experimental studies of “vertex frustrated” lattices in which some fraction of the lattice vertices do not have moments arranged in their lowest energy configuration. This novel form of frustrated system results in unusual collective behavior, including topological charges (Shakti lattice), strings of excitations that are topologically protected (Santa Fe lattice), and reduced dimensionality associated with the placement of the excited vertices (Tetris lattice). We have probed these phenomena with magnetic force microscopy and photoemission electron microscopy, using thermalization to reach the low energy collective states of the systems.

This research has been performed with many collaborators, including: Alan Albrecht, Joseph T. Batley, Nicholas S. Bingham, Daniel Bromley, Francesco Caravelli, Isaac Carrasquillo, Gia-Wei Chern, Rajesh Chopdekar, Karin Dahmen, Ayhan Duzgun, Daniel Gardeazabal, Ian Gilbert, Yuyang Lao, Brian Le, Chris Leighton, Michael Manno, Cristiano Nisoli, Liam O’Brien, Jungsik Park, Hilal Saglam, Andreas Scholl, Mohammed Sheikh, Joseph Sklenar, Shayaan Subzwari, Justin D. Watts, and Xiaoyu Zhang.

References: Gilbert et al., Physics Today 69, 54 (2016), and Nature Physics 12, 162 (2016); Nisoli et al., Nature Physics 13, 200 (2017); Lao et al., Nature Physics 14, 723 (2018); Sklenar et al., Nature Physics 15, 191 (2019); Zhang et al., arXiv:2008.07571.
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