We observe an anomalously high electric field of terahertz (THz) radiation acting on a two-dimensional electron gas (2DEG) placed beneath a thin gold film, which, however, is supposed to be opaque at THz frequencies. We show that the anomalously strong penetration of the THz electric field through a very high conductive gold film emerges if two conditions are fulfilled simultaneously: (i) the film’s thickness is less than the skin depth and (ii) the THz electric field is measured beneath the film at distances substantially smaller than the radiation wavelength. We demonstrate that under these conditions, the strength of the field acting on a 2DEG is almost the same as it would be in the absence of the gold film. The effect is detected for macroscopically homogeneous perforation-free gold films illuminated by THz laser radiation with a spot smaller than the film area. This eliminates the near field of the edge diffraction as a possible cause of the anomalous penetration. The microscopic origin of the effect remains unexplained in its details, yet. The observed effect can be used for the development of THz devices based on two-dimensional materials requiring robust highly conducting top gates placed at less than nanometer distance from the electron gas location.

中文翻译：

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通过太赫兹-不透明金膜将太赫兹电场异常强穿透到GaAs / AlGaAs量子阱中的观察

我们观察到太赫兹（THz）辐射的异常高电场作用在置于薄金膜下的二维电子气（2DEG）上，然而，该电场在THz频率下是不透明的。我们表明，如果同时满足两个条件，则通过非常高的导电金膜会出现太赫兹电场异常强的穿透力：（i）膜的厚度小于趋肤深度，并且（ii）在下面测量太赫兹电场膜的距离远小于辐射波长。我们证明了在这些条件下，作用于2DEG的电场强度几乎与没有金膜时的强度相同。对于用太赫兹激光辐射照亮的宏观均匀的无穿孔金膜检测到的效果，该点的光斑小于膜面积。这消除了边缘衍射的近场，这是异常穿透的可能原因。效果的微观原因至今仍无法解释。所观察到的效果可用于基于二维材料的THz器件的开发，该二维材料要求稳固的高导电顶栅放置在距电子气体位置小于纳米距离处。