2018/05/21 by Shun-Li Yu, Wei Wang, Zhao-Yang Dong +2 · 1 citation
Physics and Astronomy · #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.98.134410
published as Phys. Rev. B 98, 134410 (2018) · 7 pages, 6 figures
arxiv created 2018/05/21 · arxiv updated 2018/10/17
Based on the mapping between s=1/2 spin operators and hard-core bosons, we extend the cluster perturbation theory to spin systems and study the whole excitation spectrum of the antiferromagnetic J1-J2 Heisenberg model on the square lattice. In the Néel phase for J2\lesssim0.4J1, in addition to the dominant magnon excitation, there is an obvious continuum close to (π,0) in the Brillouin zone indicating the deconfined spin-1/2 spinon excitations. In the stripe phase for J2\gtrsim0.6J1, we find similar high-energy two-spinon continuums at (π/2,π/2) and (π/2,π), respectively. The intermediate phase is characterized by a spectrum with completely deconfined broad continuum, which is attributed to a Z2 quantum spin liquid with the aid of a variational-Monte-Carlo analysis.