论文标题
扫描隧道显微镜中的纵向和横向电子磁共振共振
Longitudinal and transverse electron paramagnetic resonance in a scanning tunneling microscope
论文作者
论文摘要
电子顺磁共振（EPR）光谱被广泛用于表征顺磁复合物。最近，EPR与扫描隧道显微镜（STM）结合使用，通过子角空间分辨率实现了单旋链敏感性。然而，EPR在STM中的激发机制进行了广泛的争论，这引起了人们对这种技术广泛应用的担忧。在这里，我们介绍了MGO表面上Fe和氢化Ti原子的EPR-STM的广泛实验研究和建模。我们的结果支持一种压电耦合机制，其中EPR物种在STM尖端的不均匀磁场中绝热地振荡。基于BLOCH方程与原子 - 多头计算相结合的分析可确定不同的EPR驱动力。具体而言，横向磁场梯度驱动自旋1/2氢化Ti，而纵向磁场梯度驱动Spin-2 Fe。此外，我们的结果突出了压电耦合诱导电偶极矩的潜力，从而将EPR-STM的范围扩大到非极性物种和非线性激发方案。
Electron paramagnetic resonance (EPR) spectroscopy is widely employed to characterize paramagnetic complexes. Recently, EPR combined with scanning tunneling microscopy (STM) achieved single-spin sensitivity with sub-angstrom spatial resolution. The excitation mechanism of EPR in STM, however, is broadly debated, raising concerns about widespread application of this technique. Here, we present an extensive experimental study and modelling of EPR-STM of Fe and hydrogenated Ti atoms on an MgO surface. Our results support a piezoelectric coupling mechanism, in which the EPR species oscillate adiabatically in the inhomogeneous magnetic field of the STM tip. An analysis based on Bloch equations combined with atomic-multiplet calculations identifies different EPR driving forces. Specifically, transverse magnetic-field gradients drive the spin-1/2 hydrogenated Ti, whereas longitudinal magnetic-field gradients drive the spin-2 Fe. Additionally, our results highlight the potential of piezoelectric coupling to induce electric dipole moments, thereby broadening the scope of EPR-STM to nonpolar species and nonlinear excitation schemes.
