Electronic structures and magnetism in van der Waals flat-band material Ni$_{3}$GeTe$_{2}$

TL;DR

This paper uses advanced theoretical calculations to explore the electronic and magnetic properties of Ni$_{3}$GeTe$_{2}$, revealing flat bands, complex magnetic interactions, and the effects of vacancies, advancing understanding of 2D magnetic materials.

Contribution

It demonstrates the influence of electronic correlations and geometric frustration on magnetism in Ni$_{3}$GeTe$_{2}$, highlighting its intermediate Hundness and Mottness characteristics.

Findings

Presence of flat bands due to geometric frustration

Significant spin fluctuations and paramagnetism at low temperatures

Vacancies suppress density of states at the Fermi level

Abstract

The study of magnetism in two-dimensional materials has garnered significant interest, driven by fundamental investigations into low-dimensional magnetic phenomena and their potential for applications in spintronic devices. Through dynamical mean-field theory calculations, we demonstrate that Ni$_{3}$GeTe$_{2}$ exhibits flat-band characteristics resulting from the geometric frustration of its layered triangular lattice. These flat bands are further renormalized due to electronic correlation. Our calculations reveal that the magnetic order of Ni atoms is significantly influenced by both the Coulomb interaction and Hund's coupling, indicating that the physics of Ni atoms is situated in an intermediate region between Hundness and Mottness. Additionally, our results show that Ni atoms experience significant spin fluctuations in their local moments, maintaining paramagnetism at low temperatures. Furthermore, we investigate the effect of vacancies, finding a substantial suppression of the density of states at the Fermi level. The physical mechanisms uncovered by our study provide a comprehensive understanding of the novel properties exhibited in this material.