Abstract
In the paradigm of Landau-Ginzburg-Wilson for phase and phase transitions, the spontaneous breaking of continuous symmetry leads to the appearance of the Goldstone and the Higgs mode, which correspond to the oscillation of the order parameter in both phase and amplitude channels. Although the Goldstone modes are widely seen in various quantum magnets, the observation of Higgs mode is still challenging both numerically and experimentally. Such a difference comes from the fact that the Higgs mode can decay into pairs of Goldstone modes, which cause an overdamping in the physical spectrum. In this talk, using the quantum Monte Carlo simulation and stochastic analytic continuation methods, we present a weakly-coupled Heisenberg spin chain model, and study how the Higgs mode emerges when the model is approaching the one-dimensional limit. Besides, we developed a bond correlation measurement, and find out a singlet bond mode appearing at a lower frequency than the Higgs mode in this dimensional-crossover process. Compared with the theoretical results of a chain-mean field approach and mapping to the sine-Gordon model, we find the Goldstone, the singlet bond, and the Higgs mode consist with the predictions of the solitons, first breather, and second breather from the sine-Gordon theory. These discoveries make the weakly-coupled Heisenberg spin chain model a remarkable platform to investigate the Higgs mode associated with the dimensional-crossover physics.
Reference: [1]. Chengkang Zhou, Zheng Yan, Han-Qing Wu, Kai Sun, Oleg A. Starykh, Zi Yang Meng, arXiv:2007.12715(2020) (PRL under review).
Anyone interested is welcome to attend.