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Stable Higgs Modes in Condensed Matter

Recently, a joint effort led by Postdoctoral Researcher Dr. Ying Su and Staff Scientist Dr. Shizeng Lin in Los Alamos National Laboratory and Tenure-Track Associate Prof. Yoshi Kamiya in School of Physics and Astronomy in Shanghai Jiao Tong University has demonstrated that the Higgs mode in quantum magnets, an analog of Higgs bosons in particle physics, is stable near a quantum critical point in the presence of easy-axis anisotropy. Their research paper entitled “Stable Higgs mode in anisotropic quantum magnets” was published in Physical Review B and selected as Editors’ Suggestion.

Figure 1 Schematic picture of Higgs mode and gapped-out Goldstone mode, corresponding to the amplitude fluctuation and the transverse mode, respectively (left). Dynamical structure factor featuring the Higgs mode at K point obtained by the quantum Monte Carlo simulation (right).

In condensed matter systems, the Higgs mode corresponds to the amplitude fluctuation of an order parameter that emerges as a consequence of spontaneous symmetry breaking. However, in a charge neutral system, the Higgs mode normally decays into other low-energy bosonic modes, such as the Goldstone mode, which renders the Higgs mode unstable (only visible as a smeared spectrum, e.g., in neutron scattering experiments). To overcome the difficulty of obtaining a clear signature of the Higgs mode, modified spin Hamiltonians or alternative experimental probes have been proposed and studied by different groups. Here Kamiya et al. found that easy-axis anisotropy gaps out the Goldstone magnon mode and stabilizes the Higgs mode near a quantum critical point. The results are supported by three independent approaches: a bond-operator mean-field method, field theory, and quantum Monte Carlo simulation with analytic continuation. The results suggest that the anisotropic quantum magnets provide ideal platforms to explore the Higgs physics in condensed-matter systems.

The research was supported by the National Natural Science Foundation of China (NSFC) Research Fund for International Young Scientists (No. 11950410507), the Ministry of Science and Technology (MOST) Research Fund (2016YFA0300500 and 2016YFA0300501), etc.

 

Paper link: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.102.125102

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