Spin Response and Collective Modes in Simple Metal Dichalcogenides

TL;DR

This paper investigates spin responses and collective spin-wave modes in monolayer transition metal dichalcogenides, revealing that such modes can exist even without spontaneous ferromagnetism across various doping levels and interaction strengths.

Contribution

It introduces a simple model to analyze spin responses in TMD monolayers, highlighting the existence of collective spin-wave modes independent of ferromagnetic order.

Findings

Existence of spin-wave modes at weak interactions

Modes persist without spontaneous ferromagnetism

Behavior characterized across doping and interaction ranges

Abstract

Transition metal dichalcogenide (TMD) monolayers are interesting materials in part because of their strong spin-orbit coupling. This leads to intrinsic spin-splitting of opposite signs in opposite valleys, so the valleys are intrinsically spin-polarized when hole-doped. We study spin response in a simple model of these materials, with an eye to identifying sharp collective modes (i.e, spin-waves) that are more commonly characteristic of ferromagnets. We demonstrate that such modes exist for arbitrarily weak repulsive interactions, even when they are too weak to induce spontaneous ferromagnetism. The behavior of the spin response is explored for a range of hole dopings and interaction strengths.