The development of electron spin resonance (ESR) combined with scanning tunneling spectroscopy (STM) is undoubtedly one of the main experimental breakthroughs in surface science of the last decade thanks to joining the extraordinarily high energy resolution of ESR (nano-eV scale) with the single-atom spatial resolution of STM (sub-Ångström scale). While the experimental results have significantly grown with the number of groups that have succeeded in implementing the technique, the physical mechanism behind it is still unclear, with several different mechanisms proposed to explain it. Here, we start by revising the main characteristics of the experimental setups and observed features. Then, we review the main theoretical proposals, with both their strengths and weaknesses. One of our conclusions is that many of the proposed mechanisms share the same basic principles, the time-dependent electric field at the STM junction is modulating the coupling of the spin-polarized transport electrons with the local spin. This explains why these mechanims are essentially equivalent in a broad picture. We analyze the subtle differences between some of them and how they compare with the different experimental observations.

电子自旋共振 (ESR) 与扫描隧道光谱 (STM) 相结合的发展无疑是过去十年表面科学的主要实验突破之一，这要归功于 ESR（纳米 eV 尺度）的超高能量分辨率与STM 的单原子空间分辨率（亚 Ångström 尺度）。尽管随着成功实施该技术的小组数量的增加，实验结果显着增加，但其背后的物理机制仍不清楚，提出了几种不同的机制来解释它。在这里，我们首先修改实验设置的主要特征和观察到的特征。然后，我们回顾了主要的理论建议，以及它们的优点和缺点。我们的结论之一是，许多提出的机制具有相同的基本原理，STM 结处的时间相关电场正在调节自旋极化传输电子与局部自旋的耦合。这解释了为什么这些机制在广泛的情况下本质上是等效的。我们分析了其中一些之间的细微差别，以及它们如何与不同的实验观察进行比较。