## 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.

Original language | English |
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Article number | 195135 |

Journal | Physical Review B |

Volume | 102 |

Issue number | 19 |

DOIs | |

State | Published - Nov 19 2020 |

### Bibliographical note

Funding Information:We acknowledge helpful discussions with A. Sandvik. Partial financial support was received through NSF DMR-1611161 and Keith B Macadam Graduate Excellence Fellowship. Computing resources were obtained through NSF's XSEDE award TG-DMR-140061 and the DLX computer at the University of Kentucky.

Publisher Copyright:

© 2020 American Physical Society.

## ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics