DFT+U+V Study of Magnetic Ordering in Single-Layer Pentahexoctite: Implications for Magnetic Device Platforms

TL;DR

This study uses advanced DFT calculations to explore the electronic and magnetic properties of single-layer pentahexoctite, revealing flat bands, Dirac fermions, and doping-induced magnetic transitions, positioning it as a candidate for future magnetic devices.

Contribution

It introduces the first detailed theoretical analysis of pentahexoctite's magnetic properties, including the role of flat bands and doping effects, using DFT with extended Hubbard interactions.

Findings

Discovery of nearly flat bands originating from quantum interference.

Identification of doping-induced ferrimagnetic phase transition.

Potential of pentahexoctite as an all-carbon magnetic material.

Abstract

In this work, we investigate the electronic and magnetic properties of single-layer pentahexoctite, a two-dimensional carbon allotrope patterned by pentagons, hexagons, and octagons. Using density functional theory (DFT) calculations incorporating on-site and intersite Coulomb interactions, we find that type-II Dirac Fermions are formed by a nearly flat band intersecting with a dispersive band at the Fermi level. We further examine the physical origin of nearly flat bands of pentahexoctite. Constructing ab initio tight-binding Hamiltonian based on Wannier functions, we reveal that nearly flat bands of pentahexoctite originate from quantum-mechanical destructive interference. Remarkably, our DFT calculations including extended Hubbard interactions show that hole doping induces a ferrimagnetic phase transition driven by the enhanced density of states in the nearly flat band. This finding highlights that monolayer pentahexoctite is a promising candidate for pristine all-carbon magnetic materials to serve as a platform for future magnetic and spintronic devices.