Undamped inter-valley paramagnons in doped graphene

TL;DR

This paper predicts undamped inter-valley paramagnons in doped graphene, a new type of collective spin excitation that exists below the electron-hole continuum and depends on doping levels.

Contribution

It introduces the concept of undamped inter-valley paramagnons in doped graphene and analyzes their properties and dependence on doping concentration.

Findings

Existence of undamped inter-valley paramagnons in doped graphene.

Paramagnon energy varies with doping concentration.

Paramagnons reside below the electron-hole continuum, avoiding damping.

Abstract

We predict the existence of an undamped collective spin excitation in doped graphene in the paramagnetic regime, referred to as paramagnons. Since the electrons and the holes involved in this collective mode reside in different valleys of the band structure, the momentum of these inter-valley paramagnons is given by the separation of the valleys in momentum space. The energy of the inter-valley paramagnons lies in the void region below the continuum of inter-band single-particle electron-hole excitations that appears when graphene is doped. The paramagnons are undamped due to the lack of electron-hole excitations in this void region. Their energy strongly depends on doping concentration, which can help to identify them in future experiments.