2018/07/25 by Li, Tao
#FOS: Physical sciences #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.1807.09463
We show that the best variational ground state of the spin-(1)/(2) Kagome antiferromagnetic Heisenberg model with nearest-neighboring exchange coupling(NN-KAFH) is a Z2 spin liquid state, rather than the widely believed U(1) Dirac spin liquid state. The spinon excitation in the Z2 spin liquid state has a small gap of about 1/40 of the spinon band width. We find that while the Z2 and the U(1) spin liquid state have a large overlap on finite clusters and are thus very close in energy, they host totally different spinon excitation spectrum. The strength of the RVB theory becomes particularly clear in such a situation, as it provides not only a variational understanding of the ground state structure, but also a comprehensive picture for the excitation spectrum of the system. Our result indicates that the spin-(1)/(2) NN-KAFH should be better understood as a nearly critical system, rather than a prototypical gapped Z2 spin liquid system.