Classical and quantum order in hyperkagome antiferromagnets

Abstract

Motivated by recent experiments and density functional theory calculations on choloalite PbCuTe$_2$O$_6$, which possesses a Cu-based three-dimensional hyperkagome lattice, we propose and study a $J_1$-$J_2$-$J_3$ antiferromagnetic Heisenberg model on a hyperkagome lattice. In the classical limit, possible ground states are analyzed by two triangle rules, i.e., the "hyperkagome triangle rule" and the "isolated triangle rule," and classical Monte Carlo simulations are exploited to identify possible classical magnetic ordering and explore the phase diagram. In the quantum regime, Schwinger boson theory is applied to study possible quantum spin liquid states and long-range magnetically ordered states on an equal footing. These quantum states with bosonic partons are classified and analyzed by using projective symmetry groups (PSGs). It is found that there are only four types of algebraic PSGs allowed by the space group $P4_{1}32$ on a hyperkagome lattice. Moreover, there are only two types of PSGs that are compatible with the $J_1$-$J_2$-$J_3$ Heisenberg model. These two types of $Z_2$ bosonic states are distinguished by the gauge-invariant flux on the elementary ten-site loops on the hyperkagome network, called zero-flux state and $\pi$-flux state respectively. Both the zero-flux state and the $\pi$-flux state are able to give rise to quantum spin liquid states as well as magnetically ordered states, and the zero-flux states and the $\pi$-flux states can be distinguished by the lower and upper edges of the spectral function $S(\bm{q},\omega)$, which can be measured by inelastic neutron scattering experiments.