본교 박승룡 교수와 김준경 연구원은 공동연구를 통해 Nd2Ru2O7 파이로클로르 (Pyrochlore) 고체에 라만 산란의 온도 의존성 및  편광 각도 의존성 실험을 수행하였다. 이 실험을 통해 Nd2Ru2O7 결정에서 자성 힉스 모드를 발견하였다. 이 연구 결과는 npj Quantum Materials 에 발표되었다. (자세한 내용은 아래 참고)

Title: 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 Nd2Ru2O7 at TN = 147 K and T* = 97 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 Ru4 tetrahedra. Its striking two-fold symmetry, incompatible with the underlying crystal structure, highlights the possibility of multiple entangled broken symmetries.

Authors:Dirk Wulferding, Junkyoung Kim, Mi Kyung Kim, Yang Yang, Jae Hyuck Lee, Dongjoon Song, Dongjin Oh, Heung-Sik Kim, Li Ern Chern, Yong Baek Kim, Minji Noh, Hyunyong Choi, Sungkyun Choi, Natalia B. Perkins, Changyoung Kim & Seung Ryong Park 

Link: https://www.nature.com/articles/s41535-023-00572-9