Gapless topological doublons in the periodically driven extended non-Hermitian two-particle Bose-Hubbard model
Phys. Rev. A 113, 043506 – Published 6 April, 2026
DOI: https://doi.org/10.1103/chk3-crdn
Abstract
We demonstrate the formation of Floquet doublons in the periodically driven extended non-Hermitian two-particle Bose-Hubbard model, where in the strong interaction limit an artificial manipulation of two-photon tunneling can lead to topological phase transitions. Meanwhile, both the trivial and the topological nontrivial doublon states are gapless in the low-frequency driving regime, and nontrivial topological features can be identified via the extraordinary peaks of the inverse participation ratio. In the high-frequency limit, the time-independent effective Hamiltonian is analytically obtained via the Magnus expansion, where through the transfer matrix approach we illustrate the remarkable phenomenon that the skin localization center of Floquet doublons can be turned to different sides upon changing the driving frequency, the two-particle interaction strength, or the amplitude of two-photon tunneling despite the single-boundary favored localization induced by the fixed nonreciprocal tunneling. Finally, we present that such Floquet doublons with abnormal skin localization will not penetrate to continuum due to the existence of pronounced energy gaps.
