Standard basis operator method for ground-state and temperature properties of single and two-component Bose-Hubbard model
arXiv:2607.12718
The paper develops an improved standard basis operator method to study ground‑state and finite‑temperature properties of single‑ and two‑component Bose‑Hubbard models in three dimensions, comparing results with Monte‑Carlo, tensor‑network, and experimental data, and analyzing phase‑diagram changes and first‑order transitions.
Abstract
We formulate an improved standard basis operator (SBO) method for the single and two-component Bose-Hubbard model in three dimensions. In the first case, nonzero temperature predictions are qualitatively and quantitatively enhanced by taking into account necessary number of on-site states, not just three as in previous works. Performance of the final numerical calculations is also improved by asymptotic analysis of the self-consistent equations near the critical line. Obtained results are compared with Monte-Carlo, tensor networks, Quantum Rotor Approach and experimental data. In the two-component case, SBO generalizes rather poorly, being able to account for intra-species thermal and quantum fluctuations, but not the inter-species ones. Deeper reasons for this situation are discussed. Still however, non-trivial deformation of the phase diagrams is predicted, together with first-order phase transitions steered by the changes in chemical potential.