Thermal van der Waals Interaction between Graphene Layers

TL;DR

This paper investigates the thermal van der Waals forces between graphene sheets, revealing a temperature-dependent crossover in force behavior influenced by graphene's thermal length, with implications for nanoscale interactions at room temperature.

Contribution

It introduces a finite-temperature analysis of van der Waals forces in graphene, highlighting a universal regime and the role of classical plasmons at large separations.

Findings

Force crossover from zero-temperature to thermal regime at thermal length

Thermal effects become significant at tens of nanometers at room temperature

Retardation effects are negligible in the studied regimes

Abstract

The van de Waals interaction between two graphene sheets is studied at finite temperatures. Graphene's thermal length $(\xi_T = \hbar v / k_B T)$ controls the force versus distance $(z)$ as a crossover from the zero temperature results for $z\ll \xi_T$, to a linear-in-temperature, universal regime for $z\gg \xi_T$. The large separation regime is shown to be a consequence of the classical behavior of graphene's plasmons at finite temperature. Retardation effects are largely irrelevant, both in the zero and finite temperature regimes. Thermal effects should be noticeable in the van de Waals interaction already for distances of tens of nanometers at room temperature.