Emergent many-body composite excitations of interacting spin-1/2 trimers

It was recently predicted that, in addition to well-known spinon excitations, a 1D spin-trimer chain with periodic exchange couplings hosts novel composite excitations. Bera et al. experimentally demonstrate and characterize such excitations, termed doublons and quartons, in a spin-trimer compound Na2Cu3Ge4O12. Understanding exotic forms of magnetism in quantum spin systems is an emergent topic of modern condensed matter physics. Quantum dynamics can be described by particle-like carriers of information, known-as quasiparticles that appear from the collective behaviour of the underlying system. Spinon excitations, governing the excitations of quantum spin-systems, have been accurately calculated and precisely verified experimentally for the antiferromagnetic chain model. However, identification and characterization of novel quasiparticles emerging from the topological excitations of the spin system having periodic exchange interactions are yet to be obtained. Here, we report the identification of emergent composite excitations of the novel quasiparticles doublons and quartons in spin-1/2 trimer-chain antiferromagnet Na2Cu3Ge4O12 (having periodic intrachain exchange interactions J(1)-J(1)-J(2)) and its topologically protected quantum 1/3 magnetization-plateau state. The characteristic energies, dispersion relations, and dynamical structure factor of neutron scattering as well as macroscopic quantum 1/3 magnetization-plateau state are in good agreement with the state-of-the-art dynamical density matrix renormalization group calculations.

Automated summary

Researchers experimentally demonstrate and characterize the existence of novel quasiparticles doublons and quartons in the compound Na2Cu3Ge4O12, and provide a detailed understanding of their properties.