Effective Hamiltonian of Topological Nodal Line Semimetal in Single-Component Molecular Conductor [Pd(dddt)$_2$] from First-Principles

TL;DR

This paper derives an effective Hamiltonian for a topological nodal line semimetal in a molecular conductor using first-principles calculations, providing a new analytical approach for electronic states in such materials.

Contribution

It introduces a novel 2x2 matrix Hamiltonian model for the Dirac points in a topological nodal line semimetal based on first-principles data.

Findings

Successfully models Dirac cones in [Pd(dddt)$_2$]

Provides a new method for analyzing topological nodal line semimetals

Validates the model with first-principles calculations

Abstract

Using first-principles density-functional theory calculations, we obtain the non-coplanar nodal loop for a single-component molecular conductor [Pd(dddt)$_2$] consisting of HOMO and LUMO with different parity. Focusing on two typical Dirac points, we present a model of an effective 2 $\times$ 2 matrix Hamiltonian in terms of two kinds of velocities associated with the nodal line. The base of the model is taken as HOMO and LUMO on each Dirac point, where two band energies degenerate and the off diagonal matrix element vanishes. The present model, which reasonably describes the Dirac cone in accordance with the first-principles calculation, provides a new method of analyzing electronic states of a topological nodal line semimetal.