Materials perspective on Casimir and van der Waals interactions
L. M. Woods · D. A. R. Dalvit · A. Tkatchenko · P. Rodriguez-Lopez · A. W. Rodriguez · R. Podgornik
Abstract and summary · read the original at the source
In one page
Lilia Woods, Diego Dalvit, Alexandre Tkatchenko, Pablo Rodriguez-Lopez, Alejandro Rodriguez and Rudolf Podgornik survey the whole field of forces produced by electromagnetic fluctuations, and their first move is to insist on the unification: the van der Waals force that lets a gecko hang from glass and the Casimir force between two mirrors are one phenomenon, read at different distances. What has changed in the past decade is materials. Graphene absorbs 2.3 percent of the light that falls on it, a figure fixed by the fine-structure constant alone, and that universal response gives it a Casimir force unlike a metal’s, with thermal effects that arrive far sooner. Topological insulators, Chern insulators, chiral metamaterials and sculpted geometries can turn the force from attraction to repulsion. The review’s message to its community is that this force has become a design variable: choose the material and the boundary, and you choose the sign, the strength and the reach of the vacuum’s pull.
Why it matters hereChapter two rests on the vacuum being measurable, and this is the field’s standard reference for how those measurements are made and what sets their size. Chapter six needs the next step, which this review supplies: the Casimir force is now something engineers select materials to shape, which is exactly what a vacuum energy device has to do.
What it claims
01Van der Waals and Casimir interactions are the same phenomenon at different scales — both come from electromagnetic fluctuations, both are present between any two objects of finite size at any separation, and at thermodynamic equilibrium the dipole energy of the van der Waals picture is the field energy of the Casimir picture.Section I, Introduction and Figure 1
Settled physics02The force is already an engineering fact at the small scale: it becomes measurable below a micron, it produces the stiction and adhesion that plague micro- and nano-mechanical devices, and it has been used to actuate parts of small devices without contact.Section I, Introduction
Settled physics03Graphene absorbs about 2.3 percent of incident light, a value depending only on the fine-structure constant, and that universal two-dimensional conductivity makes its Casimir interaction differ from a metal’s in sign, magnitude and distance dependence, with thermal fluctuations dominating at far smaller separations.Section III, Dirac materials beyond atomic scale separations
Published and peer-reviewed04Repulsion is reachable by choosing the boundary rather than by exotic matter: topological and Chern insulators with opposite signs of their topological parameter, chiral metamaterials, interleaved and structured geometries and objects with holes all give predicted or measured repulsive regimes, while a theorem forbids repulsion for any passive metal or dielectric metamaterial treated as an effective medium beyond its unit-cell scale.Section III.E; Sections IV and V
Published and peer-reviewed05The first Casimir measurement involving graphene, on a graphene and silica system, agreed with theory that includes the Dirac spectrum; free-standing graphene, graphene stacks, and the temperature and asymptotic behaviour are named as the measurements still missing.Section VII, Experiments probing materials aspects
Published and peer-reviewed06The open question the field states plainly is the low-frequency optical response of metals: thermal Casimir measurements have been read as favouring the Drude model in one experiment and the plasma model in others, and the isoelectronic technique, which removes the electrostatic patch corrections, is the proposed way to settle it.Section VIII, Future outlook
What to watch
Read it · abstract
Abstract
Interactions induced by electromagnetic fluctuations, such as van der Waals and Casimir forces, are of universal nature present at any length scale between any types of systems with finite dimensions. Such interactions are important not only for the fundamental science of materials behavior, but also for the design and improvement of micro- and nano-structured devices. In the past decade, many new materials have become available, which has stimulated the need of understanding their dispersive interactions. The field of van der Waals and Casimir forces has experienced an impetus in terms of developing novel theoretical and computational methods to provide new insights in related phenomena. The understanding of such forces has far reaching consequences as it bridges concepts in materials, atomic and molecular physics, condensed matter physics, high energy physics, chemistry and biology. In this review, we summarize major breakthroughs and emphasize the common origin of van der Waals and Casimir interactions. We examine progress related to novel ab initio modeling approaches and their application in various systems, interactions in materials with Dirac-like spectra, force manipulations through nontrivial boundary conditions, and applications of van der Waals forces in organic and biological matter. The outlook of the review is to give the scientific community a materials perspective of van der Waals and Casimir phenomena and stimulate the development of experimental techniques and applications.
The way in
https://doi.org/10.1103/RevModPhys.88.045003Published as Reviews of Modern Physics 88, 045003 (2016). The author copy, arXiv:1509.03338, is posted under the arXiv.org perpetual non-exclusive licence rather than a Creative Commons licence, and the APS deposit carries the APS default licence, so this page carries the summary, the claims and the authors’ own abstract and sends the reader to the source, which is free to read in full at arxiv.org/abs/1509.03338.
How to cite it
L. M. Woods, D. A. R. Dalvit, A. Tkatchenko, P. Rodriguez-Lopez, A. W. Rodriguez, R. Podgornik (2016) Materials perspective on Casimir and van der Waals interactions. doi:10.1103/RevModPhys.88.045003
Where it sits in the curriculum