Exact diagonalization studies of an effective model for quantum kagome ice

Kai-Hsin Wu^1,3*, Yi-Ping Huang², Ying-Jer Kao^1,3,4

¹Department of Physics, National Taiwan University, Taipei, Taiwan
²Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
³National Center for Theoretical Sciences, National Tsing Hua University, Hsinchu, Taiwan
⁴Department of Physics, Boston University, Massachusetts, USA

* Presenter:Kai-Hsin Wu, email:kaihsinwu@gmail.com

We study the spin-1/2 kagome Heisenberg XYZh model in the so-called quantum kagome
ice regime[1]. From our recent topological entanglement entropy and thermal entropy studies,
we find that the system does not show a Z2 topological order down to  β = 48, while the
thermal entropy down to β = 200 is consistent with the residual entropy of a classical kagome
ice in a magnetic field [2]. Using degenerate perturbation theory (DPT) out of the classical
ice manifold, we derive an effective model which shows an intricate competition between the
ring-exchange and diagonal processes. Here, we perform exact diagonalization on the effective
Hamiltonian. By tuning the weight of the diagonal term, we find that the competition can lead
to a quasi-degenerate energy spectrum, consistent with the Quantum Monte Carlo simulation
results.

[1] J. Carrasquilla, Z. Hao and R. G. Melko Nature communications 6 (2015)
[2] K.-H. Wu, Y.-P. Huang and Y.-J. Kao arXiv:1806.08145

Keywords: Quantum kagome ice, XYZh model , Quantum Monte-Carlo , Exact diagonalization