Decay and renormalization of a longitudinal mode in a quasi-two-dimensional antiferromagnet

Seung-Hwan Do; Hao Zhang; Travis J Williams; Tao Hong; V Ovidiu Garlea; J A Rodriguez-Rivera; Tae-Hwan Jang; Sang-Wook Cheong; Jae-Hoon Park; Cristian D Batista; Andrew D Christianson

doi:10.1038/s41467-021-25591-7

Decay and renormalization of a longitudinal mode in a quasi-two-dimensional antiferromagnet

Nat Commun. 2021 Sep 9;12(1):5331. doi: 10.1038/s41467-021-25591-7.

Authors

Seung-Hwan Do^#¹, Hao Zhang^#^{2

3}, Travis J Williams⁴, Tao Hong⁴, V Ovidiu Garlea⁴, J A Rodriguez-Rivera^{5

6}, Tae-Hwan Jang⁷, Sang-Wook Cheong^{7

8}, Jae-Hoon Park^{7

9}, Cristian D Batista³, Andrew D Christianson²

Affiliations

¹ Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA. doh1@ornl.gov.
² Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
³ Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA.
⁴ Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
⁵ Department of Materials Sciences, University of Maryland, College Park, MD, USA.
⁶ NIST Center for Neutron Research, Gaithersburg, MD, USA.
⁷ MPPHC-CPM, Max Planck POSTECH/Korea Research Initiative, Pohang, Republic of Korea.
⁸ Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, NJ, USA.
⁹ Department of Physics, Pohang University of Science and Technology, Pohang, Republic of Korea.

^# Contributed equally.

Abstract

An ongoing challenge in the study of quantum materials, is to reveal and explain collective quantum effects in spin systems where interactions between different modes types are important. Here we approach this problem through a combined experimental and theoretical study of interacting transverse and longitudinal modes in an easy-plane quantum magnet near a continuous quantum phase transition. Our inelastic neutron scattering measurements of Ba₂FeSi₂O₇ reveal the emergence, decay, and renormalization of a longitudinal mode throughout the Brillouin zone. The decay of the longitudinal mode is particularly pronounced at the zone center. To account for the many-body effects of the interacting low-energy modes in anisotropic magnets, we generalize the standard spin-wave theory. The measured mode decay and renormalization is reproduced by including all one-loop corrections. The theoretical framework developed here is broadly applicable to quantum magnets with more than one type of low energy mode.

Abstract

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