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

TL;DR

This paper uncovers a complex zoo of long-lived excitations, including mesons and magnons, in a doped one-dimensional spin chain, revealing rich emergent physics and proposing a strong-coupling theory for their interactions.

Contribution

It introduces a detailed study of emergent quasiparticles in a doped spin chain, including a strong-coupling theory for meson-magnon interactions, advancing understanding of low-energy excitations in doped antiferromagnets.

Findings

Identification of mesons, magnons, and tetra-parton bound states in spectra.

Development of a strong-coupling theory for meson-magnon binding.

Potential realization in quantum gas microscopes.

Abstract

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 the $t-J$ 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 ro-vibrational excitations; and tetra-parton bound states of mesons and magnons. We identify these types of quasiparticles in various spectra using DMRG 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.