Quantum-interference-induced pairing in antiferromagnetic bosonic $t$-$J$ model

The pairing mechanism in an antiferromagnetic (AFM) bosonic $t$-$J$ model is investigated via large-scale density matrix renormalization group calculations. In contrast to the competing orders in the fermionic $t$-$J$ model, we discover that a pair density wave (PDW) of tightly bound hole pairs coexists with the AFM order forming a ``supersolid'' at small doping in the bosonic model. The pairing order collapses at larger doping to a superfluid of single-boson condensation with the spin background polarized to a ferromagnetic (FM) order simultaneously. This pairing phase will disappear once a hidden quantum many-body Berry phase in the model is artificially switched off. Such a Berry phase, termed the phase string, introduces the sole ``sign problem'' in this bosonic model and imposes quantum phase frustration in the interference pattern between spin and charge degrees of freedom. Only via tightly pairing of doped holes, can such quantum frustration be most effectively erased in an AFM background. By contrast, the pairing vanishes as such a Berry phase trivializes in an FM background or is switched off by a sign-problem-free model (the Bose-Hubbard model at large $U$). The pairing mechanism proposed here is inherently quantum and many-body, stemming from exotic interference patterns caused by strong correlation effects, which is distinct from the semi-classical mechanisms based on bosonic fluctuations. Experimental schemes have been recently proposed to realize the bosonic $t$-$J$ model on ultracold Rydberg atom arrays, offering a useful platform to test the present unconventional pairing mechanism, which is also relevant to the fermionic case associated with high-temperature superconductors.
Comment: 28 pages, 4+11 figures