Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany.
Institut für Komplexe Quantensysteme and IQST, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany.
Nat Commun. 2016 Oct 6;7:13009. doi: 10.1038/ncomms13009.
The tunnelling current in scanning tunnelling spectroscopy (STS) is typically and often implicitly modelled by a continuous and homogeneous charge flow. If the charging energy of a single-charge quantum sufficiently exceeds the thermal energy, however, the granularity of the current becomes non-negligible. In this quantum limit, the capacitance of the tunnel junction mediates an interaction of the tunnelling electrons with the surrounding electromagnetic environment and becomes a source of noise itself, which cannot be neglected in STS. Using a scanning tunnelling microscope operating at 15 mK, we show that we operate in this quantum limit, which determines the ultimate energy resolution in STS. The P(E)-theory describes the probability for a tunnelling electron to exchange energy with the environment and can be regarded as the energy resolution function. We experimentally demonstrate this effect with a superconducting aluminium tip and a superconducting aluminium sample, where it is most pronounced.
在扫描隧道光谱学 (STS) 中，隧穿电流通常（并且常常隐含地）被建模为连续且均匀的电荷流。然而，如果单个电荷的充电能量大大超过热能，那么电流的粒度就变得不可忽略。在这个量子极限下，隧道结的电容介导了隧穿电子与周围电磁环境的相互作用，并成为噪声源本身，在 STS 中不能被忽略。使用在 15mK 下工作的扫描隧道显微镜，我们表明我们在此量子极限下工作，这决定了 STS 中的最终能量分辨率。P(E)-理论描述了隧穿电子与环境交换能量的概率，可以被视为能量分辨率函数。我们用超导铝尖端和超导铝样品实验性地证明了这一效应，在这种情况下，这一效应最为明显。
