Casimir and Casimir-Polder Forces in Graphene Systems: Quantum Field Theoretical Description and Thermodynamics

TL;DR

This paper reviews the quantum field theoretical approach to Casimir and Casimir-Polder forces involving graphene, analyzing low-temperature behaviors and thermodynamic consistency for various graphene parameters.

Contribution

It provides a comprehensive analysis of the low-temperature Casimir effects in graphene using the polarization tensor, including new results for zero gap and nonzero chemical potential cases.

Findings

Lifshitz theory with quantum field approach is thermodynamically consistent for graphene.

Zero gap and nonzero chemical potential case is analyzed with new findings.

Graphene with specific parameters can lead to thermodynamic anomalies.

Abstract

We review recent results on the low-temperature behaviors of the Casimir-Polder and Casimir free energy an entropy for a polarizable atom interacting with a graphene sheet and for two graphene sheets, respectively. These results are discussed in the wide context of problems arising in the Lifshitz theory of van der Waals and Casimir forces when it is applied to metallic and dielectric bodies. After a brief treatment of different approaches to theoretical description of the electromagnetic response of graphene, we concentrate on the derivation of response function in the framework of thermal quantum field theory in the Matsubara formulation using the polarization tensor in (2+1)-dimensional space-time. The asymptotic expressions for the Casimir-Polder and Casimir free energy and entropy at low temperature, obtained with the polarization tensor, are presented for a pristine graphene as well as for graphene sheets possessing some nonzero energy gap $\Delta$ and chemical potential $\mu$ under different relationships between the values of $\Delta$ and $\mu$. Along with reviewing the results obtained in the literature, we present some new findings concerning the case of zero gap and nonzero chemical potential. The conclusion is made that the Lifshitz theory of the Casimir and Casimir-Polder forces in graphene systems using the quantum field theoretical description of a pristine graphene, as well as real graphene sheets with $\Delta>2\mu$ or $\Delta<2\mu$, is consistent with the requirements of thermodynamics. The case of graphene with $\Delta=2\mu\neq 0$ leads to an entropic anomaly, but is argued to be physically unrealistic. The way to a resolution of thermodynamic problems in the Lifshitz theory based on the results obtained for graphene is discussed.