Binding of a mobile hole by an impurity potential in the t-J model: parity breaking

TL;DR

This paper investigates how a mobile hole bound by an impurity in a 2D antiferromagnet can form degenerate states of opposite parity, leading to local symmetry breaking and spiral distortions in the magnetic background.

Contribution

It demonstrates that bound states of a hole in the t-J model are parity doublets that can induce local symmetry breaking and spiral magnetic distortions.

Findings

Bound states are parity doublets with near-degenerate opposite parity.

Degeneracy leads to local symmetry breaking and spiral distortions.

Analogy with van der Waals forces in atomic physics is discussed.

Abstract

We revisit the problem of a single hole moving in the background of the two dimensional Heisenberg antiferromagnet. The hole is loosely bound by an impurity potential. We show that the bound state is generically a parity doublet: there are parametrically close bound states of opposite parity. Due to the degeneracy the bound state readily breaks local symmetries of the square lattice and this leads to formation of the long range spiral distortion of the antiferromagnetic background. A direct analogy with van der Waals forces in atomic physics is discussed.