Spin Tunneling, Berry phases and Doped Antiferromagnets

TL;DR

This paper discusses the significance of Berry phases in spin tunneling, particularly in doped antiferromagnets, and explains how the dispersion of a single hole varies with spin size, offering new insights into the t-J model.

Contribution

It highlights the role of Berry phases in doped antiferromagnets and interprets numerical results for the t-J model with different spin sizes.

Findings

Dispersion sign change at $e^{2 heta s}$ with $ heta=\pi$

Interpretation of numerical results for $s=\frac{1}{2}$

Prediction for other spin sizes

Abstract

Interference effects between Berry phase factors in spin tunneling systems have been discussed in recent Letters by Loss, DiVincenzo and Grinstein and von Delft and Henley. This Comment points out that Berry phases in spin tunneling are important in another interesting case: the two dimensional doped antiferromagnet. I show that the dispersion of a single hole in the t-J model changes sign as $e^{2\pi s}$ where $s$ is the size of the spins. This provides an interpretation of the numerical results for the $s=\half$ model, and a prediction for other spin sizes.