In conventional quasi-one-dimensional antiferromagnets with quantum spins, magnetic excitations are carried by either magnons or spinons in different energy regimes: they do not coexist independently, nor could they interact with each other. In this Letter, by combining inelastic neutron scattering, quantum Monte Carlo simulations, and random phase approximation calculations, we report the discovery and discuss the physics of the coexistence of magnons and spinons and their interactions in Botallackite-Cu2(OH)3Br. This is a unique quantum antiferromagnet consisting of alternating ferromagnetic and antiferromagnetic spin-1/2 chains with weak interchain couplings. Our study presents a new paradigm where one can study the interaction between two different types of magnetic quasiparticles: magnons and spinons.
Bibliographical noteFunding Information:
X. K. acknowledges the financial support by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under DE-SC0019259, and is grateful to Prof. G.-W Chern and Prof. A. L. Chernyshev for insightful discussions. H. Z. is supported by the National Science Foundation under DMR-1608752. T. B. and D. G. are funded by the Department of Energy through the University of Minnesota Center for Quantum Materials under DE-SC-0016371 and acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota for providing resources that contributed to the research results reported within this paper. A portion of this research used resources at both High Flux Isotope Reactor and Spallation Neutron Source, which are DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory. Z. Z. acknowledges the supports from the National Natural Science Foundation of China (Grants No. U1832166 and No. 51702320). The authors gratefully acknowledge the Gauss Centre for Supercomputing e.V. (www.gauss-centre.eu) for funding this project by providing computing time on the GCS Supercomputer SUPERMUC-NG at Leibniz Supercomputing Centre (www.lrz.de) (Project-id pr53ju). F. F. A. thanks funding from the Deutsche Forschungsgemeinschaft under the Grant No. AS 120/14-1 for the further development of the Algorithms for Lattice Fermions QMC code, as well as through the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter—ct.qmat (EXC 2147, project-id 390858490). M. R. is supported by the German Research Foundation (DFG) through Grant No. RA 2990/1-1.