arXiv quant-ph/03121842003-12-22quant-ph

电磁场起伏引起的电子束退相干

Decoherence of electron beams by electromagnetic field fluctuations

Yehoshua Levinson

DOI：: 10.1088/0305-4470/37/8/012

摘要：

电磁场起伏是固体中和真空电子束干涉中电子相干性（失相）被破坏的原因。真空涨落被导体和电子束改变，如在卡西米尔效应中，因此，光束附近的物体可以影响光束的相干性。计算了真空中两光束平行于介电常数为$ε(ω)=ε_{0}+i 4πσ/ω$的厚板运动时干涉的猝灭。在理想导体或电介质$(|ε|=\infty)$的情况下，当光束接近板的表面时，去相位被抑制，因为负责去相位的随机切向电场$E_{t}$在表面处为零。当$ε_{0}$或$σ$是有限的时，情况发生了显著的变化。在这种情况下，在表面附近存在一层，其中$E_{t}$的波动由于近场的消逝而很强。该近场层的厚度是电介质中的波长或导体中的趋肤深度的量级，对应于作为从发射器到检测器的逆电子飞行时间的频率。当电子束在这一层内时，它们的退相被增强，并且对于足够慢的电子，电子甚至可以比远离表面更强。

英文摘要：

Electromagnetic field fluctuations are responsible for the destruction of electron coherence (dephasing) in solids and in vacuum electron beam interference. The vacuum fluctuations are modified by conductors and dielectrics, as in the Casimir effect, and hence, bodies in the vicinity of the beams can influence the beam coherence. We calculate the quenching of interference of two beams moving in vacuum parallel to a thick plate with permittivity $ε(ω)=ε_{0}+i 4πσ/ω$. In case of an ideal conductor or dielectric $(|ε|=\infty)$ the dephasing is suppressed when the beams are close to the surface of the plate, because the random tangential electric field $E_{t}$, responsible for dephasing, is zero at the surface. The situation is changed dramatically when $ε_{0}$ or $σ$ are finite. In this case there exists a layer near the surface, where the fluctuations of $E_{t}$ are strong due to evanescent near fields. The thickness of this near - field layer is of the order of the wavelength in the dielectric or the skin depth in the conductor, corresponding to a frequency which is the inverse electron time of flight from the emitter to the detector. When the beams are within this layer their dephasing is enhanced and for slow enough electrons can be even stronger than far from the surface.

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英文摘要：

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