负折射率材料对Casimir效应的影响

研究了负折射率材料介质板间的Casimir效应.对于负折射率材料中由Drude-Lorentz型色散关系描述的介电常数和磁导率，色散曲线中负值频带的曲线结构由各色散吸收参数所决定，色散曲线负值频带宽度和负区域的深度等性质的变化影响了介质材料板的反射特性，进而对两材料板间的Casimir效应强弱起着重要的作用.     

含色散特异材料三明治结构的量子悬浮效应

在金属板与电介质材料板基底间插入色散特异材料板形成三明治结构,并对其Casimir作用力进行了研究.基于Casimir-Lifshitz理论,通过麦克斯韦应力张量计算了真空涨落的辐射压,并对三明治结构利用电磁模式传输矩阵方法进行了数值计算分析.计算结果表明,原本两板结构中存在的Casimir吸引力,在插入特异材料板后的三明治结构中将转变为斥力,从而使轻薄的金属板产生量子悬浮效应。讨论了特异材料板的色散电磁响应特性以及电介质板基底的影响,结果表明特异材料磁等离子频率越大、磁共振频率越小以及电介质板基底的介电常数越小时,三明治结构中获得的斥力越大.此外,板间距增加到一定范围时,三明治结构中将出现Casimir平衡回复力.特异材料填充因子越小、三明治结构中层距和层厚越大时,三明治结构间的回复力会出现在较长距的位置.三明治结构中的量子悬浮效应与平衡回复力可保证微纳米机械系统稳定性,展现出基于真空辐射压的应用前景.     

磁电超材料折射率特性分析

基于麦克斯韦旋度方程, 将磁电超材料板中的电元件和磁元件分别等效为面电流和面磁流, 通过计算这些周期性面电流和面磁流在某个磁电超材料板上产生的总电场和总磁场, 获得了关于面磁流密度和面电流密度的两个方程, 进而推导出了周期性磁电超材料折射率与磁元件的磁导率、 电元件的介电常数和空间色散项之间关系的解析公式. 与传统的折射率计算公式不同, 该解析公式充分考虑到了空间色散以及磁电超材料的电元件和磁元件的相互作用. 折射率理论曲线和基于仿真实验数据的提取值曲线能很好地符合, 这说明文中推导的折射率公式能够正确地描述磁电超材料的负折射特性. 本文的结果将为分析电磁元件之间的相互作用以及设计负折射率符合一定要求的磁电超材料提供重要的理论参考. 关键词： 磁电超材料 周期性结构 负折射率     

掺杂硅片与电磁超材料间的Casimir平衡恢复力

为探讨掺杂硅片与电磁超材料间的Casimir平衡恢复力的大小与相关材料参数间的变化关系,基于Lifshitz理论,采用格林函数得到麦克斯韦应力张量及单位面积Casimir力计算表达式,分析了掺杂硅片与电磁超材料板间的Casimir作用力.结果表明,掺杂硅片与电磁超材料板间Casimir作用力的大小和方向随着掺杂程度、材料厚度和填充比例因子的变化而改变,并能调控Casimir效应;且随着板间距的变化表现出平衡恢复力.     

掺杂硅片与电磁超材料间的Casimir平衡恢复力EI北大核心CSCD

为探讨掺杂硅片与电磁超材料间的Casimir平衡恢复力的大小与相关材料参数间的变化关系,基于Lifshitz理论,采用格林函数得到麦克斯韦应力张量及单位面积Casimir力计算表达式,分析了掺杂硅片与电磁超材料板间的Casimir作用力.结果表明,掺杂硅片与电磁超材料板间Casimir作用力的大小和方向随着掺杂程度、材料厚度和填充比例因子的变化而改变,并能调控Casimir效应;且随着板间距的变化表现出平衡恢复力.     

含负折射率材料的一维光子晶体的光学传输特性

采用光学传输矩阵方法,模拟研究了由正折射率材料和负折射率材料交替组成的一维光子晶体的光学传输特性.计算了这种含负折射率材料的一维光子晶体的透射谱和色散关系.结果表明,在正入射时,含负折射率材料的光子晶体的带隙要比传统的光子晶体要大得多,并具有狭窄的透射带,从光学薄膜理论的色散关系出发解释了形成上述现象的原因.讨论了在不同的偏振模式下,光以中心波长入射时,反射率随着入射角度的变化关系.发现含负折射率材料的一维光子晶体具有更好的角度特性,可以用来实现对中心波长的全方位反射.     

纳米器件的非零点能Casimir排斥力

结合边界元方法,利用离散点表面电流及表面磁流的格林函数得到任意三维几何体及任意材料纳米器件互相作用离散点之间的Casimir力.给出浸泡在液体中纳米器件的"非零点能"Casimir效应,分析Casimir排斥力产生的条件,为实际纳米器件之间Casimir效应分析提供新的数值方法.     

含单负材料三明治结构的电磁隧穿特性

在理论分析的基础上,结合实验研究了单负材料/正折射率材料(或单负材料)/单负材料三明治结构的电磁隧穿性质.这种结构的电磁隧穿来源于入射平面波与结构的表面或体极化激元的耦合,从理论上讨论并计算了正入射情况下这种结构中的极化激元的色散关系.发现:由单负材料作为边界而正折射率材料为中间层的三明治结构具有体极化激元,这种极化激元的共振频率随着中间层厚度的增加向低频移动;由不同性质的单负材料构成的三明治结构具有两条色散曲线,这两条色散曲线随着中间层厚度的增加而简并.随后基于L-C传输线技 关键词： 单负材料 极化激元 隧穿 L-C传输线')" href="#">L-C传输线     

周期性层状铁氧体-电介质复合材料中导模模式的有效负折射率

运用等效传输线法研究了周期性层状铁氧体-电介质/金属复合材料导模模式的有效折射率.通过对复合材料导模模式的色散特性和有效折射率的分析和计算，发现负折射率只能出现在TE模式激励下的某一频带内.在负折射率频带内的电磁损耗与复合材料中介电材料的性质密切相关，减小介电损耗可以有效降低复合材料的损耗，但过分小的介电损耗则会导致负折射率的消失. 关键词： 负折射率 导模模式 等效传输线法     

含负折射率介质非线性Bragg腔的双稳态特性

研究了含负折射率介质一维光子晶体非线性Bragg腔的透射特性、光学增强和双稳态特性.对负折射率介质无色散和有色散非线性Bragg腔及由两种正折射率介质构成的非线性Bragg腔的透射谱、光学增强、缺陷模的线宽、入射光的红移量、双稳态开关阈值进行了比较.含负折射率介质的非线性Bragg腔可显著增大腔内光学增强效应,降低缺陷模的线宽、入射光的红移量和双稳态开关阈值.     

Repulsive Casimir forces

We discuss repulsive Casimir forces between dielectric materials with nontrivial magnetic susceptibility. It is shown that considerations based on the naive pairwise summation of van der Waals and Casimir-Polder forces may not only give an incorrect estimate of the magnitude of the total Casimir force but even the wrong sign of the force when materials with high dielectric and magnetic responses are involved. Indeed repulsive Casimir forces may be found in a large range of parameters, and we suggest that the effect may be realized in known materials. The phenomenon of repulsive Casimir forces may be of importance both for experimental study and for nanomachinery applications.     

Repulsive Casimir force between gyroelectric slabs

We obtain the repulsive Casimir force between two parallel gyroelectric slabs, thus overcoming the difficulty that the repulsive Casimir force is difficult to achieve in a naturally occurring material. Under practically realizable parameters, we realize the crossover from attractive (repulsive) to repulsive (attractive) forces by changing either the external static magnetic field, the background permittivity of the gyroelectric medium, the slab’s thickness or the gap between the slabs. The proposed configuration, unlike the artificial metamaterial one, does not require the careful design of the material’s micro-structure, and hence is expected to be a practical candidate for obtaining a repulsive Casimir force.     

Casimir-Lifshitz theory and metamaterials

Based on a generalization of the Lifshiftz theory, we calculate Casimir forces involving magnetodielectric and possibly anisotropic metamaterials, focusing on the possibility of repulsive forces. It is found that Casimir repulsion decreases with magnetic dissipation, and even a small Drude background in metallic-based metamaterials acts to make attractive a Casimir force that would otherwise be predicted to be repulsive. The sign of the force also depends sensitively on the degree of optical anisotropy of the metamaterial and on the form of the frequency dependency of the magnetic response.     

Attractive and repulsive Casimir vacuum energy with general boundary conditions

The infrared behaviour of quantum field theories confined in bounded domains is strongly dependent on the shape and structure of space boundaries. The most significant physical effect arises in the behaviour of the vacuum energy. The Casimir energy can be attractive or repulsive depending on the nature of the boundary. We calculate the vacuum energy for a massless scalar field confined between two homogeneous parallel plates with the most general type of boundary conditions depending on four parameters. The analysis provides a powerful method to identify which boundary conditions generate attractive or repulsive Casimir forces between the plates. In the interface between both regimes we find a very interesting family of boundary conditions which do not induce any type of Casimir force. We also show that the attractive regime holds far beyond identical boundary conditions for the two plates required by the Kenneth–Klich theorem and that the strongest attractive Casimir force appears for periodic boundary conditions whereas the strongest repulsive Casimir force corresponds to anti-periodic boundary conditions. Most of the analysed boundary conditions are new and some of them can be physically implemented with metamaterials.     

Attractive Casimir forces in a closed geometry

We study the Casimir force acting on a conducting piston with arbitrary cross section. We find the exact solution for a rectangular cross section and the first three terms in the asymptotic expansion for small height to width ratio when the cross section is arbitrary. Though weakened by the presence of the walls, the Casimir force turns out to be always attractive. Claims of repulsive Casimir forces for related configurations, like the cube, are invalidated by cutoff dependence.     

Opposites attract: a theorem about the Casimir Force

We consider the Casimir interaction between (nonmagnetic) dielectric bodies or conductors. Our main result is a proof that the Casimir force between two bodies related by reflection is always attractive, independent of the exact form of the bodies or dielectric properties. Apart from being a fundamental property of fields, the theorem and its corollaries also rule out a class of suggestions to obtain repulsive forces, such as the two hemisphere repulsion suggestion and its relatives.     

The asymptotic behavior of Casimir force in the presence of compactified universal extra dimensions

The Casimir effect for parallel plates in the presence of compactified universal extra dimensions within the frame of Kaluza–Klein theory is analyzed. Having regularized and discussed the expressions of Casimir force in the limit, we show that the nature of Casimir force is repulsive if the distance between the plates is large enough and the higher-dimensional spacetime is, the greater the value of repulsive Casimir force between plates is. The repulsive nature of the force is not consistent with the experimental phenomena.     

Tunable Casimir repulsion with three-dimensional topological insulators

In this Letter, we show that switching between repulsive and attractive Casimir forces by means of external tunable parameters could be realized with two topological insulator plates. We find two regimes where a repulsive (attractive) force is found at small (large) distances between the plates, canceling out at a critical distance. For a frequency range where the effective electromagnetic action is valid, this distance appears at length scales corresponding to 1 - ?(ω) ～ (2/π)αθ.     

Repulsive and attractive Casimir forces between magnetodielectric slabs

The Casimir force between two parallel magnetodielectric slabs is investigated by means of Casimir–Lifshitz Theory. For two magnetodielectric slabs, one is permittivity-negative, while the other is permeability-negative in the real frequency space. Numerical results show that when the separation between these two slabs is small (or large), the Casimir force is repulsive, while for the intermediate separation, the Casimir force is attractive. As a consequence, there are two equilibria with zero Casimir force, and a repulsive–attractive–repulsive transition takes place with increasing the separation. Therefore, if the separation between two interacting slabs is manipulated in the small (or large) separation region, it is possible to overcome the stiction in micromechanical and nanomechanical systems.     

Fermat原理在左手媒质中的推广

 在考虑左、右手媒质定义对比基础上,定义了广义折射率,并对Fermat原理的表述进行了推广。从电磁理论出发,得到了折射率的具体表示。广义的折射率可以通过媒质电参数有效地表现理想及人工复合左、右手媒质中折射的负正特性。以此所得理论可以有效描述由左、右手媒质所共同构成的折射率可变的混合稳态电磁或光学传输系统。讨论了折射率的高频形式,并对负折射现象进行了讨论。