Quasiparticle energy bands and Fermi surfaces of monolayer NbSe$_2$

TL;DR

This paper uses first-principles $GW$ calculations to analyze the quasiparticle energy bands and Fermi surfaces of monolayer NbSe$_2$, revealing the effects of self-energy corrections and spin-orbit interactions on electronic properties and charge density wave formations.

Contribution

It introduces a comprehensive $GW$-based analysis of monolayer NbSe$_2$, including a tight-binding model that accurately reproduces quasiparticle bands and Fermi surfaces, and discusses implications for CDW transitions.

Findings

Self-energy corrections increase band width and alter Fermi surface shape.

Spin-orbit interaction significantly impacts Fermi surface and quasiparticle bands.

The tight-binding model accurately reproduces $GW$ quasiparticle features.

Abstract

A quasiparticle band structure of a single layer 2H-NbSe$_2$ is reported by using first-principles $GW$ calculation. We show that a self-energy correction increases the width of a partially occupied band and alters its Fermi surface shape when comparing those using conventional mean-field calculation methods. Owing to a broken inversion symmetry in the trigonal prismatic single layer structure, the spin-orbit interaction is included and its impact on the Fermi surface and quasiparticle energy bands are discussed. We also calculate the doping dependent static susceptibilities from the band structures obtained by the mean-field calculation as well as $GW$ calculation with and without spin-orbit interactions. A complete tight-binding model is constructed within the three-band third nearest neighbour hoppings and is shown to reproduce our $GW$ quasiparticle energy bands and Fermi surface very well. Considering variations of the Fermi surface shapes depending on self-energy corrections and spin-orbit interactions, we discuss the formations of charge density wave (CDW) with different dielectric environments and their implications on recent controversial experimental results on CDW transition temperatures.