Anomalous growth of thermoelectric power in gapped graphene

TL;DR

This paper investigates how a small energy gap in graphene can cause a significant, anomalous increase in thermoelectric power near the gap edge, driven by impurity scattering effects.

Contribution

It reveals the emergence of a giant Seebeck signal bump in gapped graphene due to impurity scattering, extending understanding of thermoelectric behavior in modified graphene.

Findings

Giant Seebeck bump appears near the gap edge.

Nonmonotonous dependence of thermopower on chemical potential.

Failure of the simple Mott formula in gapped graphene.

Abstract

There exist experiments indicating that at certain conditions, such as an appropriate substrate, a gap of the order of 10 meV can be opened at the Dirac points of a quasiparticle spectrum of graphene. We demonstrate that the opening of such a gap can result in the appearance of a fingerprint bump of the Seebeck signal when the chemical potential approaches the gap edge. The magnitude of the bump can be up to one order higher than the already large value of the thermopower occurring in graphene. Such a giant effect, accompanied by the nonmonotonous dependence on the chemical potential, is related to the emergence of a new channel of quasiparticle scattering from impurities with the relaxation time strongly dependent on the energy. We analyze the behavior of conductivity and thermopower in such a system, accounting for quasiparticle scattering from impurities with the model potential in a self-consistent scheme. Reproducing the existing results for the case of gapless graphene, we demonstrate a failure of the simple Mott formula in the case under consideration.