Classical to quantum crossover of the cyclotron resonance in graphene: A study of the strength of intraband absorption

TL;DR

This paper investigates the classical-to-quantum transition of cyclotron resonance in highly-doped graphene through magneto-transmission experiments, revealing renormalization effects linked to electron interactions and quasiparticle velocity.

Contribution

It provides the first direct measurement of the Drude weight in graphene and demonstrates its renormalization due to electron-electron interactions, confirming theoretical predictions.

Findings

Drude weight is renormalized compared to non-interacting models

Quasiparticle velocity is enhanced and linked to Drude weight renormalization

Experimental results agree with recent theoretical models

Abstract

We report on absolute magneto-transmission experiments on highly-doped quasi-free-standing epitaxial graphene targeting the classical-to-quantum crossover of the cyclotron resonance. This study allows us to directly extract the carrier density and also other relevant quantities such as the quasiparticle velocity and the Drude weight, which is precisely measured from the strength of the cyclotron resonance. We find that the Drude weight is renormalized with respect to its non-interacting (or random-phase-approximation) value and that the renormalization is tied to the quasiparticle velocity enhancement. This finding is in agreement with recent theoretical predictions, which attribute the renormalization of the Drude weight in graphene to the interplay between broken Galilean invariance and electron-electron interactions.