Disorder induced loss of magnetization in Lieb's graphene quantum dots

TL;DR

This study investigates how disorder impacts the magnetization stability in Lieb graphene quantum dots, revealing a critical disorder level that causes magnetization loss and differences in effects based on disorder type and edge structure.

Contribution

It provides new insights into the disorder-induced magnetization loss in Lieb GQDs, analyzing effects of bulk and edge disorder across various shapes and edge lengths.

Findings

Critical disorder strength causes magnetization loss.

Bulk disorder affects states away from Fermi level.

Edge disorder impacts states near Fermi level.

Abstract

The stability of the magnetization in Lieb graphene quantum dots (GQD) against disorder is studied. Such systems exhibit the degenerate shell of edge states in the middle of the energy gap occupied by spin polarized electrons. Disorder affects the energy spectrum and leads to the removal of the degeneracy, and in a consequence the loss of the magnetization. We find that there is a critical value of disorder strength over which the magnetization starts dropping. We first consider GQDs with different shapes and edge termination and compare the effect of bulk and edge disorder. We find that bulk disorder influences the energy spectrum far away from the Fermi level while edge disorder affects states in the vicinity of it. We next focus on Lieb GQDs with a single zigzag edge. The stability of the ferromagnetic order against disorder strength is analyzed for structures with a different edge length. The probability of getting maximal spin polarization is determined.