Abstract
Polarized inelastic neutron scattering experiments recently identified the amplitude (Higgs) mode in , a two-dimensional near-quantum-critical spin- two-leg ladder compound, which exhibits a weak easy-axis exchange anisotropy. Here, we theoretically examine the dynamic spin structure factor of such planar coupled spin-ladder systems using large-scale quantum Monte Carlo simulations. This allows us to provide a quantitative account of the experimental neutron scattering data within a consistent quantum spin model. Moreover, we trace the details of the continuous evolution of the amplitude mode from a two-particle bound state of coupled ladders in the classical Ising limit all the way to the quantum spin- Heisenberg limit with fully restored SU(2) symmetry, where it gets overdamped by the two-magnon continuum in neutron scattering.
- Received 22 December 2018
DOI:https://doi.org/10.1103/PhysRevLett.122.127201
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