Phase diagram of the frustrated quantum-XY model on the honeycomb lattice studied by series expansions: Evidence for proximity to a bicritical point

作者：Oitmaa J^*; Singh R R P

来源：Physical Review B, 2014, 89(10): 104423.

DOI：10.1103/PhysRevB.89.104423

We study the nearest-neighbor exchange (J(1)) and second-nearest-neighbor exchange (J(2)) XY antiferromagnet on the honeycomb lattice using ground state series expansions around Neel, columnar, and dimer phases. The conventional two-sublattice XY Neel order at small J(2) vanishes at J(2)/J(1) = 0.22 +/- 0.01 in agreement with results from density matrix renormalization group (DMRG) studies. Near the transition, we find evidence for an approximate emergent symmetry between XY and Ising degrees of freedom, namely the nearest-neighbor Ising and XY spin correlations become nearly equal. This suggests that the system is close to a bicritical point separating XY and Ising orders. At still larger J(2)/J(1) the columnar and dimer energies are found to be nearly degenerate. At even larger J(2) the columnar phase is obtained. The ground state energies in all three phases are in good agreement with the values found in the DMRG studies.

• 出版日期2014-3-27