We calculate the Casimir interaction between a sphere and a plate, both described by the plasma model, the Drude model, or generalizations of the two models. We compare the results at both zero and finite temperatures. At asymptotically large separations we obtain analytical results for the interaction that reveal a non-universal, i.e., material dependent interaction for the plasma model. The latter result contains the asymptotic interaction for Drude metals and perfect reflectors as different but universal limiting cases. This observation is related to the screening of a static magnetic field by a London superconductor. For small separations we find corrections to the proximity force approximation (PFA) that support correlations between geometry and material properties that are not captured by the Lifshitz theory. Our results at finite temperatures reveal for Drude metals a non-monotonic temperature dependence of the Casimir free energy and a negative entropy over a sizeable range of separations.
We derive an exact analytic expression for the high-temperature limit of the Casimir interaction between two Drude spheres of arbitrary radii. Specifically, we determine the Casimir free energy by using the scattering approach in the plane-wave basis. Within a round-trip expansion, we are led to consider the combinatorics of certain partitions of the round trips. The relation between the Casimir free energy and the capacitance matrix of two spheres is discussed. Previously known results for the special cases of a sphere-plane geometry as well as two spheres of equal radii are recovered. An asy…
Casimir-Foucault interaction: Free energy and entropy at low temperature
最近发现,在由Drude模型描述的金属之间的Casimir效应中出现的热力学异常可以归因于波动的Foucault(或涡流)电流的相互作用[Phys. Rev. Lett. 103,130405(2009)]。我们明确地表明,两个领导项的低温修正的Casimir自由能的两个板块之间的相互作用,是相同的那些有关的福柯电流相互作用单独的,这是非常小的良好的金属的校正。此外,沿实际频率的模式密度被引入,示出的Casimir自由能,由Lifshitz理论给出的,在一个自然的方式分离的涡流和传播腔模式的贡献,分别。长期以来,人们一直认为后者对低温卡西米尔异常的重要性不大。这令人信服地表明,涡流模式是负责大的温度修正德鲁德金属之间的Casimir效应,预测由Lifshitz理论,但在实验中没有观察到。
Comment on "Anomalous temperature dependence of the Casimir force for thin metal films" [arXiv:0712.1395]
最近,A。Yampol'skii,S. Savel'ev,Z. A. Mayselis,S. S. Apostolov和F.海苔[Phys. Rev. Lett.,101,096803(2008),arXiv:0712.1395]声称,由Drude模型描述的薄金属膜和理想金属半空间之间的Casimir力可以随温度降低,而对于体样品,Casimir力随温度增加。在此基础上,提出了薄膜与块状理想金属之间Casimir力大小随温度变化的实验观测结果。我们表明,与作者所声称的相反,Casimir力的大小随温度的降低在一个宽的温度区域的散装样品所描述的德鲁德模型。这种减少被证明是远远大于一个薄膜,它已经被实验排除。
We study the acoustic Casimir pressure between imperfectly reflecting plates immersed in various isotropic noise backgrounds. Unlike the case of perfect reflectors, the force tends to strong repulsion at small plate separations due to the existence of modes between the plates. Additionally, in a noise field of constant spectral intensity, the large-bandwidth limit of the pressure has a reflectivity-dependent sensitivity to the infrared cutoff; we uncover the associated singular behavior as the product of the reflection coefficients approaches 1, which is intimately connected to a tendency of c…