Sensory organ like response determines the magnetism of zigzag-edged honeycomb nanoribbons

TL;DR

This paper develops an analytical theory for the magnetic behavior of zigzag-edged honeycomb nanoribbons, revealing a unique sensory organ-like response influencing magnetism, with implications for nanostructure design and doping effects.

Contribution

It introduces a novel analytical framework considering sensory organ-like responses, extending understanding beyond traditional theories, and demonstrates the robustness of magnetism through variational Monte-Carlo simulations.

Findings

Edge magnetic moment varies as ln U

First order magnetic transition depends on doping and width

Magnetism is robust to fluctuations

Abstract

We present an analytical theory for the magnetic phase diagram for zigzag edge terminated honeycomb nanoribbons described by a Hubbard model with an interaction parameter U . We show that the edge magnetic moment varies as ln U and uncover its dependence on the width W of the ribbon. The physics of this owes its origin to the sensory organ like response of the nanoribbons, demonstrating that considerations beyond the usual Stoner-Landau theory are necessary to understand the magnetism of these systems. A first order magnetic transition from an anti-parallel orientation of the moments on opposite edges to a parallel orientation occurs upon doping with holes or electrons. The critical doping for this transition is shown to depend inversely on the width of the ribbon. Using variational Monte-Carlo calculations, we show that magnetism is robust to fluctuations. Additionally, we show that the magnetic phase diagram is generic to zigzag edge terminated nanostructures such as nanodots. Furthermore, we perform first principles modeling to show how such magnetic transitions can be realized in substituted graphene nanoribbons.