Holes as Dipoles in a Doped Antiferromagnet and Stripe Instabilities

TL;DR

This paper models doped holes in antiferromagnetic Mott insulators as dipoles, showing they tend to localize and form stripe patterns due to dipole interactions, leading to inhomogeneity and phase competition.

Contribution

It introduces a dipole-based effective model for doped holes, revealing their role in stripe formation and inhomogeneity in antiferromagnetic materials.

Findings

Doped holes induce localized dipole-like spin configurations.

Long-range dipole interactions drive stripe instabilities.

Stripe phases include metallic and insulating types.

Abstract

Based on an effective model of a doped antiferromagnetic Mott insulator, we show that a doped hole will induce a dipole-like spin configuration in a spin ordered phase at low doping. The kinetic energy of doped holes is severely frustrated and a hole-dipole object is actually localized or self-trapped in space. Without a balance from the kinetic energy, the long-range dipole-dipole interaction between doped holes will dominate the low-energy physics, leading to an inhomogeneity instability as hole-dipoles collapse into stripes. Both antiphase metallic stripes of quarter-filling and antiphase insulating stripes along a diagonal direction are discussed as composed of hole-dipoles as elementary building blocks. Stripe melting and competing phases are also discussed.