Collective magnetic Higgs excitation in a pyrochlore ruthenate
Abstract
The emergence of scalar Higgs-type amplitude modes in systems where symmetry is spontaneously broken has been a highly successful, paradigmatic description of phase transitions, with implications ranging from high-energy particle physics to low-energy condensed matter systems. Here, we uncover two successive high temperature phase transitions in the pyrochlore magnet NdRuO at K and K, that lead to giant phonon instabilities and culminate in the emergence of a highly coherent excitation. This coherent excitation, distinct from other phonons and from conventional magnetic modes, stabilizes at a low energy of 3 meV. We assign it to a collective Higgs-type amplitude mode, that involves bond energy modulations of the Ru tetrahedra. Its striking two-fold symmetry, incompatible with the underlying crystal structure, highlights the possibility of multiple entangled broken symmetries.
Cite
@article{arxiv.2204.12124,
title = {Collective magnetic Higgs excitation in a pyrochlore ruthenate},
author = {Dirk Wulferding and Junkyeong Kim and Mi Kyung Kim and Yang Yang and Jae Hyuck Lee and Dongjoon Song and Dongjin Oh and Heung-Sik Kim and Li Ern Chern and Yong Baek Kim and Minji Noh and Hyunyong Choi and Sungkyun Choi and Natalia B. Perkins and Changyoung Kim and Seung Ryong Park},
journal= {arXiv preprint arXiv:2204.12124},
year = {2023}
}