Multiband Transport in Bilayer Graphene at High Carrier Densities

TL;DR

This study investigates multiband transport in bilayer graphene at high carrier densities, revealing the filling of high energy subbands and associated changes in resistance and oscillations, with detailed measurements of carrier properties.

Contribution

It demonstrates the filling of high energy subbands in bilayer graphene at high densities using a polymer electrolyte gate, and characterizes their transport properties.

Findings

High energy subbands are populated at carrier densities ≥ 2.4×10^{13} cm^{-2}.

A sudden resistance increase and new SdH oscillations occur upon subband filling.

Higher energy bands exhibit mobilities at least twice those of lower energy bands.

Abstract

We report a multiband transport study of bilayer graphene at high carrier densities. Employing a poly(ethylene)oxide-CsClO$_4$ solid polymer electrolyte gate we demonstrate the filling of the high energy subbands in bilayer graphene samples at carrier densities $|n|\geq2.4\times 10^{13}$ cm$^{-2}$. We observe a sudden increase of resistance and the onset of a second family of Shubnikov de Haas (SdH) oscillations as these high energy subbands are populated. From simultaneous Hall and magnetoresistance measurements together with SdH oscillations in the multiband conduction regime, we deduce the carrier densities and mobilities for the higher energy bands separately and find the mobilities to be at least a factor of two higher than those in the low energy bands.