Spin Chains with Periodic Array of Impurities

TL;DR

This paper studies a spin chain model with a periodic array of two types of spins, analyzing its low-energy phases and properties using rigorous theorems and effective field theory methods.

Contribution

It introduces a unified approach to study spin chains with impurities and alternating spins through rigorous and field-theoretic analysis.

Findings

Identification of massive and massless phases in the model

Mapping to non-linear sigma model clarifies low-energy behavior

Rigorous application of Lieb-Shultz-Mattis theorem

Abstract

We investigate the spin chain model composed of periodic array of two kinds of spins $S_1$ and $S_2$, which allows us to study the spin chains with impurities as well as the alternating spin chains in a unified fashion. By using the Lieb-Shultz-Mattis theorem, we first study the model rigorously, and then by mapping it to the non-linear sigma model, we extensively investigate low-energy properties with particular emphasis on the competition between the massive and massless phases.