Temperature Dependence of Electric Transport in Few-layer Graphene under Large Charge Doping Induced by Electrochemical Gating

TL;DR

This study investigates how electric transport in multi-layer graphene varies with temperature under high charge doping, revealing electron-electron and electron-phonon scattering behaviors and a surprising independence from charge density.

Contribution

It provides new experimental data on temperature-dependent transport in multi-layer graphene at high doping levels using a novel electrolyte gating method.

Findings

Low-temperature T^2 dependence suggests electron-electron scattering.

Crossover to electron-phonon regime occurs around 100 K.

Crossover temperature is independent of charge density.

Abstract

The temperature dependence of electric transport properties of single-layer and few-layer graphene at large charge doping is of great interest both for the study of the scattering processes dominating the conductivity at different temperatures and in view of the theoretically predicted possibility to reach the superconducting state in such extreme conditions. Here we present the results obtained in 3-, 4- and 5-layer graphene devices down to 3.5 K, where a large surface charge density up to about 6.8x10^14 cm^(-2) has been reached by employing a novel polymer electrolyte solution for the electrochemical gating. In contrast with recent results obtained in single-layer graphene, the temperature dependence of the sheet resistance between 20 K and 280 K shows a low-temperature dominance of a T^2 component - that can be associated with electron-electron scattering - and, at about 100 K, a crossover to the classic electron-phonon regime. Unexpectedly this crossover does not show any dependence on the induced charge density, i.e. on the large tuning of the Fermi energy.