The Higgs Mode of Planar Coupled Spin-Ladders and its Observation in C${}_9$H${}_{18}$N${}_2$CuBr${}_4$

Abstract

Polarized inelastic neutron scattering experiments recently identified the amplitude (Higgs) mode in C${}_9$H${}_{18}$N${}_2$CuBr${}_4$, a two-dimensional near-quantum-critical spin-1/2 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 trance 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-1/2 Heisenberg limit with fully restored SU(2) symmetry, where it gets overdamped by the two-magnon continuum in neutron scattering.

9 pages, 10 figures

References in corpus (8)

• Solving the 3d Ising Model with the Conformal Bootstrap II. c-Minimization and Precise Critical Exponents
• Amplitude / Higgs Modes in Condensed Matter Physics
• Generalized Directed Loop Method for Quantum Monte Carlo Simulations
• The Higgs mode in a two-dimensional superfluid
• Direct observation of the Higgs amplitude mode in a two-dimensional quantum antiferromagnet near the quantum critical point
• Universal Properties of the Higgs Resonance in (2+1)-Dimensional U(1) Critical Systems
• Critical capacitance and charge-vortex duality near the superfluid to insulator transition
• Magnetic ordering induced by interladder coupling in the spin-1/2 Heisenberg two-leg ladder antiferromagnet C${}_9$H${}_{18}$N${}_2$CuBr${}_4$