On dielectric screening in twisted double bilayer graphene

TL;DR

This study investigates dielectric screening effects in twisted double bilayer graphene with a 5-degree mismatch angle, revealing distinct carrier density behaviors and estimating a screening length slightly larger than in AB-stacked graphene.

Contribution

It provides the first experimental analysis of dielectric screening in twisted double bilayer graphene and introduces a theoretical model for charge decay with a specific screening length.

Findings

Quantum oscillations from two bands observed

Carrier density behavior differs from AB-stacked graphene

Screening length estimated to be slightly larger

Abstract

We have studied the dielectric screening of electric field which is induced by a gate voltage in twisted double bilayer graphene by using a sample with a mismatch angle of about 5 degrees. In low temperature magnetotransport measurements, quantum oscillations of magnetoresistance originating from two bands with different carrier density were observed. The behavior of the carrier densities with respect to the total carrier density were distinct from that of the AB-stacked tetralayer graphene. The carrier density ratio was theoretically analyzed in terms of the model that the induced charge decays exponentially with distance with a screening length {\lambda}. The estimated {\lambda} was slightly larger than that of AB-stacked graphene, which would possibly reflect the difference in the inter-plane distribution of probability of the wave function.