Ferromagnetic nodal-line metal in monolayer {\em h}-InC

TL;DR

This paper predicts a stable, ferromagnetic monolayer { extit h}-InC with unique electronic properties, including coexistence of nodal lines and electron-hole pockets, tunable by spin-orbit coupling and magnetization direction.

Contribution

The study introduces a new 2D ferromagnetic material, { extit h}-InC, with exotic Fermi surface topology and tunable nodal lines, supported by first-principles calculations.

Findings

Multiple nodal lines coexist in the electronic structure.

Spin-orbit coupling enables tuning of nodal lines into topological points.

{ extit h}-InC exhibits stable ferromagnetism and exotic band topology.

Abstract

Based on first-principles calculations, we predict a new two-dimensional ferromagnetic material that exhibits exotic Fermi surface topology. We show that monolayer hexagonal indium carbide ({\em h}-InC) is thermodynamically and dynamically stable, and it energetically favors the ferromagnetic ordering of spins. The perfectly planar geometry in two dimensions, together with ferromagnetism, gives rise to a unique opportunity to encounter intriguing electronic properties, captured in the Fermi surface and band topology. We show that multiple nodal lines coexist in momentum space, accompanied by the electron and hole pockets that touch each other linearly at the nodal lines. Inclusion of spin-orbit coupling enriches the magnetic and electronic properties of {\em h}-InC. Spin-orbit coupling leads to an easy-plane type magnetocrystalline anisotropy, and the nodal lines can be tuned into topological nodal points, contingent upon the magnetization direction. Symmetry analysis and a tight-binding model are provided to explain the nodal structure of the bands. Our findings suggest {\em h}-InC as a new venue for supporting carbon-based magnetism and exotic band topology in two dimensions.