Analogues of light and gravity in the collective excitations of quantum magnets*

Condensed matter systems offer parallels to some of the most important phenomena in high-energy physics, exemplified by the Anderson-Higgs transition in superconductors and magnetic monopoles in spin ice. Here we ask whether similar parallels exist between the fundamental force carrying particles of electromagnetism and gravity and the collective excitations of quantum magnets.

Using a combination of analytic methods and semi-classical molecular dynamics simulation, we first revisit the analogy between photons and the massless spin-1 Goldstone modes of antiferromagnets. We then consider the linearly dispersing, spin-2 Goldstone modes of a quantum magnet with quadrupolar order, arguing that these provide an analogue to gravitational waves. Through explicit simulation, we show how the quadrupole waves of a spin-1 magnet can mimic the gravitational radiation observed from binary mergers of black holes.