Level spectroscopy in a two-dimensional quantum magnet: Linearly dispersing spinons at the deconfined quantum critical point

Abstract

We study the level structure of excitations at the "deconfined" critical point separating antiferromagnetic and valence-bond-solid phases in two-dimensional quantum spin systems using the $J$-$Q$ model as an example. Energy gaps in different spin ($S$) and momentum ($\mathbf{k}$) sectors are extracted from imaginary-time correlation functions obtained in quantum Monte Carlo simulations. We find strong quantitative evidence for deconfined linearly dispersing spinons with gapless points at $\mathbf{k}=(0,0)$, $(\pi ,0)$, $(0,\pi )$, and $(\pi ,\pi )$, as inferred from two-spinon excitations ($S=0$ and $S=1$ states) around these points. We also observe a duality between singlet and triplet excitations at the critical point and inside the ordered phases, in support of an enhanced symmetry, possibly SO(5).

9 pages with 13 figures

References in corpus (7)

• "Deconfined" quantum critical points
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• From an Antiferromagnet to a Valence Bond Solid: Evidence for a First Order Phase Transition
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Cited by in corpus (4)

• Nearly deconfined spinon excitations in the square-lattice spin-1/2 Heisenberg antiferromagnet
• Deconfined quantum criticality in spin-1/2 chains with long-range interactions
• Dual dynamic scaling in deconfined quantum criticality
• Self-dual criticality in three-dimensional ${\mathbb{Z}}_2$ gauge theory with matter