Low-energy spectra in the t-J type models at light doping

TL;DR

This paper proposes a variational approach revealing two types of low-energy states in t-J models at low doping, explaining anomalous results from exact diagonalization studies through spin-bag and quasi-particle states.

Contribution

It introduces a novel variational framework identifying two low-energy states in t-J models, enhancing understanding of their properties at low doping.

Findings

Identification of spin-bag states with suppressed antiferromagnetic order

Existence of a continuum of low-energy excitations involving separated spin and charge

Explanation of anomalous results from small-cluster exact diagonalization studies

Abstract

Based on a variational approach, we propose that there are two kinds of low energy states in the t-J type models at low doping. In a quasi-particle state an unpaired spin bound to a hole with a well-defined momentum can be excited with spin waves. The resulting state shows a suppression of antiferromagnetic order around the hole with the profile of a {\em spin bag}. These spin-bag states with spin and charge or hole separated form a continuum of low-energy excitations. Very different properties predicted by these two kinds of states explain a number of anomalous results observed in the exact diagonalization studies on small clusters up to 32 sites.