Fermionic algebraic quantum spin liquid in an octa-kagome frustrated antiferromagnet
Cheng Peng,1 Shi-Ju Ran,2 Tao Liu,1 Xi Chen,1 and Gang Su 1,3,*
1Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, School of Physical Sciences,
University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
2ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
3Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
(Received 12 September 2016; revised manuscript received 23 December 2016; published 22 February 2017)
We investigate the ground state and finite-temperature properties of the spin-1/2 Heisenberg antiferromagnet on an infinite octa-kagome lattice by utilizing state-of-the-art tensor network-based numerical methods. It is shown that the ground state has a vanishing local magnetization and possesses a 1/2-magnetization plateau with an up-down-up-up spin configuration. A quantum phase transition at the critical coupling ratio Jd/Jt = 0.6 is found. When 0 < Jd/Jt < 0.6, the system is in a valence bond state, where an obvious zero-magnetization plateau is observed, implying a gapful spin excitation; when Jd/Jt > 0.6, the system exhibits a gapless excitation, in which the dimer-dimer correlation is found decaying in a power law, while the spin-spin and chiral-chiral correlation functions decay exponentially. At the isotropic point (Jd/Jt = 1), we unveil that at low temperature T , the specific heat depends linearly on T , and the susceptibility tends to a constant for T → 0, giving rise to a Wilson ratio around unity, implying that the system under interest is a fermionic algebraic quantum spin liquid.