Higgs mode and its decay in a two-dimensional antiferromagnet

By A. Jain, M. Krautloher, J. Porras, G. Ryu, D. P. Chen, D. Abernathy, Jitae T. Park, A. Ivanov, J. Chaloupka, G. Khaliullin and 2 more. Nature Physics, 2017

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An inelastic neutron scattering study of the two-dimensional antiferromagnet Ca2RuO4 reveals evidence for a condensed-matter analogue of the Higgs mode, and its subsequent decay into transverse Goldstone modes. Condensed-matter analogues of the Higgs boson in particle physics allow insights into its behaviour in different symmetries and dimensionalities1. Evidence for the Higgs mode has been reported in a number of different settings, including ultracold atomic gases2, disordered superconductors3, and dimerized quantum magnets4. However, decay processes of the Higgs mode (which are eminently important in particle physics) have not yet been studied in condensed matter due to the lack of a suitable material system coupled to a direct experimental probe. A quantitative understanding of these processes is particularly important for low-dimensional systems, where the Higgs mode decays rapidly and has remained elusive to most experimental probes. Here, we discover and study the Higgs mode in a two-dimensional antiferromagnet using spin-polarized inelastic neutron scattering. Our spin-wave spectra of Ca2RuO4 directly reveal a well-defined, dispersive Higgs mode, which quickly decays into transverse Goldstone modes at the antiferromagnetic ordering wavevector. Through a complete mapping of the transverse modes in the reciprocal space, we uniquely specify the minimal model Hamiltonian and describe the decay process. We thus establish a novel condensed-matter platform for research on the dynamics of the Higgs mode.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics

View Paper: https://www.semanticscholar.org/paper/86e79019ae39ab949dba2ef82b11595797c44ae6