The amplitude mode in three-dimensional dimerized antiferromagnets

TL;DR

This study uses advanced quantum Monte Carlo simulations and analytic continuation to explore the Higgs amplitude mode in a 3D dimerized antiferromagnet, confirming theoretical scaling and revealing detailed dynamical properties.

Contribution

It combines QMC and stochastic analytic continuation to characterize the amplitude mode in a 3D quantum spin system, providing new insights into its spectral properties.

Findings

Both spin and dimer spectral functions follow field-theoretical scaling near the critical point.

The spin response line width matches neutron scattering data on TlCuCl₃.

The dimer response is significantly broader than the spin response.

Abstract

The amplitude (Higgs) mode is a ubiquitous collective excitation related to spontaneous breaking of a continuous symmetry. We combine quantum Monte Carlo (QMC) simulations with stochastic analytic continuation to investigate the dynamics of the amplitude mode in a three-dimensional dimerized quantum spin system. We characterize this mode by calculating the spin and dimer spectral functions near the quantum critical point, finding that both the energies and the intrinsic widths satisfy field-theoretical scaling predictions. While the line width of the spin response is close to that observed in neutron scattering experiments on TlCuCl$_3$, the dimer response is significantly broader. Our results demonstrate that highly non-trivial dynamical properties are accessible by modern QMC and analytic continuation methods.