Symmetry enhanced first-order phase transition in a two-dimensional quantum magnet

Bowen Zhao; Phillip Weinberg; Anders W. Sandvik

doi:10.1038/s41567-019-0484-x

paper

Symmetry enhanced first-order phase transition in a two-dimensional quantum magnet

arXiv:1804.07115 · doi:10.1038/s41567-019-0484-x

Abstract

Theoretical studies of quantum phase transitions have suggested critical points with higher symmetries than those of the underlying Hamiltonian. Here we demonstrate a surprising emergent symmetry of the coexistence state at a strongly discontinuous phase transition between two ordered ground states. We present a quantum Monte Carlo study of a two-dimensional $S = 1/2$ quantum magnet hosting the antiferromagnetic (AFM) and plaquette-singlet solid (PSS) states recently detected in SrCu $_{2}$ (BO $_{3}$ ) $_{2}$ . We observe that the O(3) symmetric AFM order and the Z $_{2}$ symmetric PSS order form an O(4) vector at the transition. The control parameter $g$ (a coupling ratio) rotates the vector between the AFM and PSS sectors and there are no energy barriers between the two at the transition point $g_{c}$ . This phenomenon may be observable in SrCu $_{2}$ (BO $_{3}$ ) $_{2}$ .

12 pages, 12 figures