First-order phase transitions in the square-lattice easy-plane J-Q model
Abstract
We study the quantum phase transition between the superfluid and valence bond solid in easy-plane J-Q models on the square lattice. The Hamiltonian we study is a linear combination of two model Hamiltonians: (1) an SU(2) symmetric model, which is the well known J-Q model that does not show any direct signs of a discontinuous transition on the largest lattices and is presumed continuous and (2) an easy-plane version of the J-Q model, which shows clear evidence for a first-order transition even on rather small lattices of size L ≈16 . A parameter 0 ≤λ ≤1 [λ =0 being the easy-plane model and λ =1 being the SU(2) symmetric J-Q model] allows us to smoothly interpolate between these two limiting models. We use stochastic series expansion (SSE) quantum Monte Carlo (QMC) to investigate the nature of this transition as λ is varied—here we present studies for λ =0 ,0.5 ,0.75 ,0.85 ,0.95 , and 1. While we find that the first-order transition weakens as λ is increased from 0 to 1, we find no evidence that the transition becomes continuous until the SU(2) symmetric point, λ =1 . We thus conclude that the square-lattice superfluid-VBS transition in the two-component easy-plane model is generically first order.
- Publication:
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Physical Review B
- Pub Date:
- November 2020
- DOI:
- 10.1103/PhysRevB.102.195135
- arXiv:
- arXiv:1909.12357
- Bibcode:
- 2020PhRvB.102s5135D
- Keywords:
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- Condensed Matter - Strongly Correlated Electrons
- E-Print:
- Phys. Rev. B 102, 195135 (2020)