Inelastic electron tunneling spectroscopy for probing strongly correlated many-body systems by scanning tunneling microscopy
Inelastic electron tunneling spectroscopy for probing strongly correlated many-body systems by scanning tunneling microscopy
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DOI：
10.1103/physrevb.101.125405
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发表时间：
2019-10
影响因子：
3.7
通讯作者：
Fabian Eickhoff;Elena Kolodzeiski;T. Esat;N. Fournier;C. Wagner;Thorsten Deilmann;R. Temirov;M. Ro
中科院分区：
文献类型：
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作者：
Fabian Eickhoff;Elena Kolodzeiski;T. Esat;N. Fournier;C. Wagner;Thorsten Deilmann;R. Temirov;M. Ro
我们提出了扫描隧道显微镜（STM）隧道理论的扩展，包括不同类型的振动电子耦合，这些耦合在强耦合极限下对隧道电流产生非弹性贡献。它可以更好地理解金属基底上分子的更复杂的扫描隧道光谱，以分离弹性和非弹性贡献。起点是在没有 STM 尖端的情况下电子活性局部轨道的光谱函数的精确解。这包括由分子和基底组成的耦合系统中的电子-声子耦合到任意顺序，包括反绝热强耦合机制以及对分子自由电子自旋的近藤效应。隧道电流是根据隧道矩阵元素的二阶导出的，该矩阵元素以相关振动位移的幂展开。我们使用单粒子电子特性从头计算的结果作为数值重正化群方法的适应材料特定输入，以准确确定 Ag(111) 上 NTCDA 分子的电子特性，作为我们理论的具有挑战性的样本系统。我们的分析表明，在没有任何电子声子耦合到实验扫描隧道光谱的情况下，隧道电流的从头算多体计算之间的不匹配可以通过包括两种机制来解决：（i）局部基底轨道上的强非常规荷斯坦项导致近藤温度降低，以及（ii）与 隧道矩阵元负责有限频率下 $dI/dV$ 曲线中的非弹性阶跃。
We present an extension of the tunneling theory for scanning tunneling microcopy (STM) to include different types of vibrational-electronic couplings responsible for inelastic contributions to the tunnel current in the strong-coupling limit. It allows for a better understanding of more complex scanning tunneling spectra of molecules on a metallic substrate in separating elastic and inelastic contributions. The starting point is the exact solution of the spectral functions for the electronic active local orbitals in the absence of the STM tip. This includes electron-phonon coupling in the coupled system comprising the molecule and the substrate to arbitrary order including the anti-adiabatic strong coupling regime as well as the Kondo effect on a free electron spin of the molecule. The tunneling current is derived in second order of the tunneling matrix element which is expanded in powers of the relevant vibrational displacements. We use the results of an ab-initio calculation for the single-particle electronic properties as an adapted material-specific input for a numerical renormalization group approach for accurately determining the electronic properties of a NTCDA molecule on Ag(111) as a challenging sample system for our theory. Our analysis shows that the mismatch between the ab-initio many-body calculation of the tunnel current in the absence of any electron-phonon coupling to the experiment scanning tunneling spectra can be resolved by including two mechanisms: (i) a strong unconventional Holstein term on the local substrate orbital leads to reduction of the Kondo temperature and (ii) a different electron-vibrational coupling to the tunneling matrix element is responsible for inelastic steps in the $dI/dV$ curve at finite frequencies.