Malavolti Luigi, McMurtrie Gregory, Rolf-Pissarczyk Steffen, Yan Shichao, Burgess Jacob A J, Loth Sebastian
Institute for Functional Matter and Quantum Technologies, University of Stuttgart, 70569 Stuttgart, Germany.
Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany and Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany.
Nanoscale. 2020 Jun 4;12(21):11619-11626. doi: 10.1039/c9nr10252c.
Minimizing the invasiveness of scanning tunneling measurements is paramount for observation of the magnetic properties of unperturbed atomic-scale objects. We show that the invasiveness of STM inspection on few-atom spin systems can be drastically reduced by means of a remote detection scheme, which makes use of a sensor spin weakly coupled to the sensed object. By comparing direct and remote measurements we identify the relevant perturbations caused by the local probe. For direct inspection we find that tunneling electrons strongly perturb the investigated object even for currents as low as 3 pA. Electrons injected into the sensor spin induce perturbations with much reduced probability. The sensing scheme uses standard differential conductance measurements, and is decoupled both by its non-local nature, and by dynamic decoupling due to the significantly different time scales at which the sensor and sensed object evolve. The latter makes it possible to effectively remove static interactions between the sensed object and the spin sensor while still allowing the spin sensing. In this way we achieve measurements with a reduction in perturbative effects of up to 100 times relative to direct scanning tunneling measurements, which enables minimally invasive measurements of a few-atom magnet's fragile spin states with STM.
对于观察未受干扰的原子尺度物体的磁性而言，将扫描隧道测量的侵入性降至最低至关重要。我们表明，通过一种远程检测方案，可以大幅降低扫描隧道显微镜（STM）对少数原子自旋系统检测的侵入性，该方案利用了与被检测物体弱耦合的传感器自旋。通过比较直接测量和远程测量，我们确定了由局部探针引起的相关扰动。对于直接检测，我们发现即使电流低至3 pA，隧穿电子也会强烈扰动被研究物体。注入传感器自旋的电子引起扰动的概率要小得多。该传感方案使用标准的微分电导测量，并且由于其非局部性质以及传感器和被检测物体演化的时间尺度显著不同而实现动态解耦，从而得以动态解耦。后者使得在仍允许自旋传感的同时，能够有效消除被检测物体与自旋传感器之间的静态相互作用。通过这种方式，我们实现了相对于直接扫描隧道测量而言，微扰效应降低多达100倍的测量，这使得利用STM对少数原子磁体的脆弱自旋态进行微创测量成为可能。
