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 . A parameter [ being the easy-plane model and 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 is varied—here we present studies for , and 1. While we find that the first-order transition weakens as is increased from 0 to 1, we find no evidence that the transition becomes continuous until the SU(2) symmetric point, . We thus conclude that the square-lattice superfluid-VBS transition in the two-component easy-plane model is generically first order.
3 More- Received 21 September 2020
- Revised 29 October 2020
- Accepted 30 October 2020
DOI:https://doi.org/10.1103/PhysRevB.102.195135
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