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December 25, 2010

Repulsive casimir force from metamaterials

Repulsive Casimir forces with finite-thickness slabs

We use the extended Lifshitz theory to study the behaviors of the Casimir forces between finite-thickness effective medium slabs. We first study the interaction between a semi-infinite Drude metal and a finite-thickness magnetic slab with or without substrate. For no substrate, the large distance d dependence of the force is repulsive and goes as 1/d^5; for the Drude metal substrate, a stable equilibrium point appears at an intermediate distance which can be tuned by the thickness of the slab. We then study the interaction between two identical chiral metamaterial slabs with and without substrate. For no substrate, the finite thickness of the slabs D does not influence significantly the repulsive character of the force at short distances, while the attractive character at large distances becomes weaker and behaves as 1/d^6; for the Drude metal substrate, the finite thickness of the slabs D does not influence the repulsive force too much at short distances until D=0.05\lambda_0.



Repulsive Casimir force was also found to be realized by using chiral metamaterials (CMMs) if the chirality is strong enough.

Arxiv - Microstructure Effects for Casimir Forces in Chiral Metamaterials

We examine a recent prediction for the chirality-dependence of the Casimir force in chiral metamaterials by numerical computation of the forces between the exact microstructures, rather than homogeneous approximations. We compute the exact force for a chiral bent-cross pattern, as well as forces for an idealized "omega"-particle medium in the dilute approximation and identify the effects of structural inhomogeneity (i.e. proximity forces and anisotropy). We find that these microstructure effects dominate the force for separations where chirality was predicted to have a strong influence. To get observations of chirality free from microstructure effects, one must go to large separations where the effect of chirality is at most sim10^{-4} of the total force.

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