Ground-state van der Waals forces in planar multilayer magnetodielectrics

Casimir force between dispersive magnetodielectrics

We extend our approach to the Casimir effect between absorbing dielectric multilayers [M. S. Tomas, Phys. Rev. A 66, 052103 (2002)] to magnetodielectric systems. The resulting expression for the force is used to numerically explore the effect of the medium dispersion on the attractive/repulsive force in a metal-magnetodielectric system described by the Drude-Lorentz permittivities and permeabilities.

Casimir-Polder interaction between an atom and a small magnetodielectric sphere

On the basis of macroscopic quantum electrodynamics and point-scattering techniques, we derive a closed expression for the Casimir-Polder force between a ground-state atom and a small magnetodielectric sphere in an arbitrary environment. In order to allow for the presence of both bodies and media, local-field corrections are taken into account. Our results are compared with the known van der Waals force between two ground-state atoms. To continuously interpolate between the two extreme cases of a single atom and a macroscopic sphere, we also derive the force between an atom and a sphere of var…

Vacuum force on an atom in a magnetodielectric cavity

We demonstrate that, according to a recently suggested Lorentz-force approach to the Casimir effect, the vacuum force on an atom embedded in a material cavity differs substantially from the force on an atom of the cavity medium. The force on an embedded atom is of the familiar (van der Waals and Casimir-Polder) type, however, more strongly modified by the cavity medium than usually considered. The force on an atom of the cavity medium is of the medium-assisted force type with rather unusual properties, as demonstrated very recently [M. S. Tomas, Phys. Rev. A 71, 060101(R) (2005)]. This implies…

Casimir-Polder interaction of atoms with magnetodielectric bodies

A general theory of the Casimir-Polder interaction of single atoms with dispersing and absorbing magnetodielectric bodies is presented, which is based on QED in linear, causal media. Both ground-state and excited atoms are considered. Whereas the Casimir-Polder force acting on a ground-state atom can conveniently be derived from a perturbative calculation of the atom-field coupling energy, an atom in an excited state is subject to transient force components that can only be fully understood by a dynamical treatment based on the body-assisted vacuum Lorentz force. The results show that the Casi…

Van der Waals interactions between excited atoms in generic environments

We consider the the van der Waals force involving excited atoms in general environments, constituted by magnetodielectric bodies. We develop a dynamical approach studying the dynamics of the atoms and the field, mutually coupled. When only one atom is excited, our dynamical theory suggests that for large distances the van der Waals force acting on the ground-state atom is monotonic, while the force acting in the excited atom is spatially oscillating. We show how this latter force can be related to the known oscillating Casimir--Polder force on an excited atom near a (ground-state) body. Our fo…

Body-assisted van der Waals interaction between two atoms

Using fourth-order perturbation theory, a general formula for the van der Waals potential of two neutral, unpolarized, ground-state atoms in the presence of an arbitrary arrangement of dispersing and absorbing magnetodielectric bodies is derived. The theory is applied to two atoms in bulk material and in front of a planar multilayer system, with special emphasis on the cases of a perfectly reflecting plate and a semi-infinite half space. It is demonstrated that the enhancement and reduction of the two-atom interaction due to the presence of a perfectly reflecting plate can be understood, at le…

金与薄磁电介质板之间增强的排斥性卡西米尔力

Enhanced repulsive Casimir forces between gold and thin magnetodielectric plates

本研究计算金属与磁性板间的排斥卡西米尔力，探究板厚、低频电磁参数及温度的调控作用，发现薄磁板满足μ(0)≥ε(0)时存在排斥力，可实现亚微米间距排斥，有望用现有高分辨率技术测量。

Medium effects on the van der Waals force

We consider the van der Waals interaction between two ground-state atoms embedded in adjacent semi-infinite magnetodielectric media, with emphasis on medium effects on it. We demonstrate that, in this case, at small atom-atom distances the van der Waals interaction is screened by the surrounding media in the same way as in an effective (single) medium. At larger atomic distances, however, its dependence on the material parameters of the system and the positions of the atoms is more complex. We also calculate the Casimir-Polder potential of an atom A arising from a uniform distribution of atoms…

Microscopic origin of Casimir-Polder forces

We establish a general relation between dispersion forces. First, based on QED in causal media, leading-order perturbation theory is used to express both the single-atom Casimir-Polder and the two-atom van der Waals potentials in terms of the atomic polarizabilities and the Green tensor for the body-assisted electromagnetic field. Endowed with this geometry-independent framework, we then employ the Born expansion of the Green tensor together with the Clausius-Mosotti relation to prove that the macroscopic Casimir-Polder potential of an atom in the presence of dielectric bodies is due to an inf…

Lifshitz theory of van der Waals pressure in dissipative media

We derive a first--principles method of determining the van der Waals or Casimir pressure in a dissipative and dispersive planar multilayered system by calculating the Maxwell stress tensor in a fictitious layer of vacuum, that is eventually made to vanish, introduced in the structure. This is illustrated by calculating the van der Waals pressure in a thin film with dissipative properties embedded between two semi--infinite media.

未对准系统中的切向卡西米尔力：磁介质、真实导体与扭矩

Tangential Casimir force in the misaligned system: Magnetic media, real conductors, and a torque

该研究拓展了未对准平行板的切向卡西米尔力至磁介质范畴，分析了真实导体的温度相关切向力，还提出了各向同性介质平行板的卡西米尔扭矩，为不带电表面扭矩实现提供了简易途径。

耗散稀释在实现范德华谐振子高机械品质因子中的作用

Role of dissipation dilution in achieving high mechanical quality factors in van der Waals resonators

本研究针对范德华材料未利用耗散稀释提升机械品质因子的问题，采用无聚合物剥离技术制备单层MoS₂鼓，结合耗散稀释模型分析损耗机制，实现了4K下单层MoS₂鼓的高品质因子，证实耗散稀释是实现高机械品质因子的关键机制，为原子级薄谐振器用于量子传感等提供了平台。