Higgs and Goldstone spin-wave modes in striped magnetic texture
Matías P. Grassi, Moritz Geilen, Kosseila Aït Oukaci, Y. Henry, D. Lacour, D. Stoeffler, M. Hehn, Philipp Pirro, Matthieu Bailleul
Abstract
Spontaneous symmetry breaking is ubiquitous in physics. Its spectroscopic signature consists in the softening of a specific mode upon approaching the transition from the high-symmetry side and its subsequent splitting into a zero-frequency Goldstone mode and a nonzero-frequency Higgs mode. Although they determine the whole system dynamics, these features are difficult to address in practice because of their vanishing coupling to most experimental probes and/or their strong interaction with other fluctuations. In this paper, we consider a periodic magnetic modulation occurring in a ferromagnetic film with perpendicular-to-plane magnetic anisotropy and observe its Goldstone and Higgs spin-wave modes at room temperature using microwave and optical techniques. This simple system constitutes a particularly convenient platform for further exploring the dynamics of symmetry breaking.