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arXiv · 1804.07115

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

Bowen Zhao·Phillip Weinberg·Anders W. Sandvik
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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$_3$)$_2$.

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Bowen Zhao, Phillip Weinberg, Anders W. Sandvik. 2018-04-19. Symmetry enhanced first-order phase transition in a two-dimensional quantum magnet. https://doi.org/10.1038/s41567-019-0484-x

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