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.