Effect of charged impurities on graphene thermoelectric power near the Dirac point

TL;DR

This study investigates how charged impurities affect the thermoelectric power in graphene near the Dirac point, revealing the limitations of the Mott relation in high-mobility samples and confirming its validity in low-mobility samples.

Contribution

The paper demonstrates the failure of the Mott relation near the Dirac point in high-mobility graphene and provides a theoretical explanation that aligns with experimental data.

Findings

Mott relation fails near the Dirac point in high-mobility graphene.

Mott relation holds at all gate voltages in low-mobility graphene.

High-temperature effects are crucial for accurate theoretical modeling.

Abstract

In graphene devices with a varying degree of disorders as characterized by their carrier mobility and minimum conductivity, we have studied the thermoelectric power along with the electrical conductivity over a wide range of temperatures. We have found that the Mott relation fails in the vicinity of the Dirac point in high-mobility graphene. By properly taking account of the high temperature effects, we have obtained good agreement between the Boltzmann transport theory and our experimental data. In low-mobility graphene where the charged impurities induce relatively high residual carrier density, the Mott relation holds at all gate voltages.