Many-body localization and particle multioccupancy in the disordered Bose-Hubbard model

Jie Chen; Chun Chen; Xiaoqun Wang

doi:10.1103/q5l5-517x

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arXiv · 2503.03712

Many-body localization and particle multioccupancy in the disordered Bose-Hubbard model

Jie Chen·Chun Chen·Xiaoqun Wang

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Abstract

We study the potential influence of the particle multi-occupations on the stability of many-body localization in the disordered Bose-Hubbard model. Within the higher-energy section of the dynamical phase diagram, we find that there is no apparent finite-size boundary drift between the thermal phase and the many-body localized regime. We substantiate this observation by introducing the Van Vleck perturbation theory into the field of many-body localization. The appropriateness of this method rests largely on the peculiar Hilbert-space structure enabled by the particles' Bose statistics. The situation is reversed in the lower-energy section of the dynamical phase diagram, where the significant finite-size boundary drift pushes the putative many-body localized regime up to the greater disorder strengths. We utilize the algebraic projection method to make a connection linking the disordered Bose-Hubbard model in the lower-energy section to an intricate disordered spin chain model. This issue of the finite-size drift could hence be analogous to what happens in the disordered Heisenberg chain. Both trends might be traced back to the particles' intrinsic or emergent single-occupancy constraint like the spin-$1/2$, hard-core boson, or spinless fermion degrees of freedom.

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Jie Chen, Chun Chen, Xiaoqun Wang. 2025-03-05. Many-body localization and particle multioccupancy in the disordered Bose-Hubbard model. https://doi.org/10.1103/q5l5-517x

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