Particle zoo in a doped spin chain: Correlated states of mesons and magnons

It is a widely accepted view that the interplay of spin and charge degrees of freedom in doped antiferromagnets (AFMs) gives rise to the rich physics of high-temperature superconductors. Nevertheless, it remains unclear how effective low-energy degrees of freedom and the corresponding field theories emerge from microscopic models, including t - J and Hubbard Hamiltonians. A promising view comprises that the charge carriers have a rich internal parton structure on intermediate scales, but the interplay of the emergent partons with collective magnon excitations of the surrounding AFM remains unexplored. Here we study a doped one-dimensional spin chain in a staggered magnetic field and demonstrate that it supports a zoo of various long-lived excitations. These include magnons, mesonic pairs of spinons and chargons along with their rovibrational excitations, and tetraparton bound states of mesons and magnons. We identify these types of quasiparticles in various spectra using density-matrix renormalization group simulations. Moreover, we introduce a strong-coupling theory describing the polaronic dressing and molecular binding of mesons to collective magnon excitations. The effective theory can be solved by standard tools developed for polaronic problems and can be extended to study similar physics in two-dimensional doped AFMs in the future. Experimentally, the doped spin-chain in a staggered field can be directly realized in quantum gas microscopes.

Automated summary

It is unclear how effective low-energy degrees of freedom and the corresponding field theories emerge from microscopic models in doped antiferromagnets. This study demonstrates the existence of various long-lived excitations in a doped one-dimensional spin chain in a staggered magnetic field, including magnons, mesonic pairs, and tetraparton bound states. The introduction of a strong-coupling theory allows for the analysis of the polaronic dressing and molecular binding of mesons to collective magnon excitations. The experimental realization of this system can be achieved in quantum gas microscopes.