Magnetic monopole polarons in artificial spin ices

¹ Department of Physics, University of Virginia - Charlottesville, VA 22904, USA
² Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory Los Alamos, NM 87545, USA
³ Department of Engineering and Sciences, Universidad Adolfo Ibáñez - Santiago, Chile

Received: 12 March 2016
Accepted: 6 May 2016

Abstract

Emergent quasiparticles that arise from the fractionalization of the microscopic degrees of freedom have been one of the central themes in modern condensed-matter physics. The notion of magnetic monopoles, freely moving quasiparticles fragmented from local dipole excitations, has enjoyed much success in understanding the thermodynamic, static, and transport properties of the so-called spin-ice materials. The artificial version of spin ice, where a lattice of nanoscale magnetic dipoles is sculpted out of a ferromagnetic film, provides a unique opportunity to study these unusual quasiparticles in a material-by-design approach. Here we show that the elementary excitations in the ice phase of a nano-magnetic array arranged in the pentagonal lattice are composite objects comprised of the emergent monopole and a surrounding cloud of opposite uncompensated magnetic charges.