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arXiv · 2009.12393

Valence-Bond Order in a Honeycomb Antiferromagnet Coupled to Quantum Phonons

Manuel Weber
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Abstract

We use exact quantum Monte Carlo simulations to demonstrate that the N\'eel ground state of an antiferromagnetic SU(2) spin-$\frac{1}{2}$ Heisenberg model on the honeycomb lattice can be destroyed by a coupling to quantum phonons. We find a clear first-order transition to a valence-bond-solid state with Kekul\'e order instead of a deconfined quantum critical point. However, quantum lattice fluctuations can drive the transition towards weakly first-order, revealing a tunability of the transition by the retardation of the interaction. In contrast to the one-dimensional case, our phase diagram in the adiabatic regime is qualitatively different from the frustrated $J_1$-$J_2$ model. Our results suggest that a coupling to bond phonons can induce Kekul\'e order in Dirac systems.

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Manuel Weber. 2020-09-25. Valence-Bond Order in a Honeycomb Antiferromagnet Coupled to Quantum Phonons. https://doi.org/10.1103/physrevb.103.l041105

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