The Signature of Magnetic Monopoles

Most magnets have north and south poles. One exception, however, is a quantum spin ice, a magnetic material that hosts excitations that behave like monopoles—tiny magnets with a single pole. While researchers know monopoles exist, they lack a firm prediction of their signatures in measurements. Masafumi Udagawa at Gakushuin University, Japan, and Roderich Moessner at the Max Planck Institute for Complex Systems in Germany have now calculated the neutron-scattering signature of pairs of monopoles in a quantum spin ice. The signature contains a set of sharp and asymmetric spectral features that the duo says should be experimentally accessible.