Spectroscopy and Dynamics of a Two-Dimensional Electron Gas on Ultrathin Helium Films on Cu(111).
Spectroscopy and Dynamics of a Two-Dimensional Electron Gas on Ultrathin Helium Films on Cu(111).
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Cu(111) 超薄氦膜上二维电子气的光谱学和动力学
DOI：
10.1103/physrevlett.116.256801
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发表时间：
2016
影响因子：
8.6
通讯作者：
P. Feulner
中科院分区：
文献类型：
--
作者：
N. Armbrust;J. Güdde;U. Höfer;S. Kossler;P. Feulner
氦原子表面的像势态电子是二维电子气的一个独特的模型系统。在这里，我们调查他们的性质在极端情况下减少膜厚度：一个单层的氦物理吸附在单晶（111）取向的铜表面。为此，我们利用了定制的设置时间分辨双光子光电发射在非常低的温度下，在真空条件下。我们表明，高度极化的金属基板的第一（）图像的潜在状态的结合能增加超过2个数量级相比，液氦的表面。在这种状态下的电子仍然强烈地从金属表面去耦，由于氦的大的负电子亲和力，我们发现，即使是1个单层的氦增加其寿命的1个数量级相比，裸Cu（111）表面。
Electrons in image-potential states on the surface of bulk helium represent a unique model system of a two-dimensional electron gas. Here, we investigate their properties in the extreme case of reduced film thickness: a monolayer of helium physisorbed on a single-crystalline (111)-oriented Cu surface. For this purpose we have utilized a customized setup for time-resolved two-photon photoemission at very low temperatures under ultrahigh vacuum conditions. We demonstrate that the highly polarizable metal substrate increases the binding energy of the first () image-potential state by more than 2 orders of magnitude as compared to the surface of liquid helium. An electron in this state is still strongly decoupled from the metal surface due to the large negative electron affinity of helium and we find that even 1 monolayer of helium increases its lifetime by 1 order of magnitude compared to the bare Cu(111) surface.