Quantum phase diagram of a frustrated antiferromagnet on the bilayer honeycomb lattice

TL;DR

This paper maps the quantum phase diagram of a frustrated spin-1/2 Heisenberg antiferromagnet on a bilayer honeycomb lattice, revealing four distinct phases including three magnetic orders and one quantum disordered dimer phase.

Contribution

It provides a comprehensive analysis of the phase diagram using multiple methods, identifying a quantum disordered phase connected to an exact singlet ground state.

Findings

Identified four distinct phases in the model.

Discovered a quantum disordered interlayer dimer phase.

Connected the dimer phase to an exact singlet ground state.

Abstract

We study the spin-1/2 Heisenberg antiferromagnet on a bilayer honeycomb lattice including interlayer frustration. Using a set of complementary approaches, namely Schwinger bosons, dimer series expansion, bond operators, and exact diagonalization, we map out the quantum phase diagram. Analyzing ground state energies and elementary excitation spectra, we find four distinct phases, corresponding to three collinear magnetic long range ordered states, and one quantum disordered interlayer dimer phase. We detail, that the latter phase is adiabatically connected to an "exact" singlet product ground state of the the bilayer which exists along a line of maximum interlayer frustration. The order within the remaining three phases will be clarified.