Influence of vibrational modes on quantum transport through a nanodevice
Influence of vibrational modes on quantum transport through a nanodevice
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DOI：
10.1103/physrevb.87.195112
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发表时间：
2013-02
影响因子：
3.7
通讯作者：
A. Jovchev;F. Anders
中科院分区：
文献类型：
--
作者：
A. Jovchev;F. Anders
我们使用最近提出的散射态数值重整化群（SNRG）方法来计算$I(V)$和通过单个分子水平耦合到局部分子声子的微分电导。我们还讨论了该模型的平衡物理性质，并证明了低能哈密顿量是由一个有效的相互作用共振能级模型给出的。从NRG能级流中，我们直接提取了有效电荷转移尺度$\Gamma_{\rm eff}$和分子能级与引线电子之间的动态诱导电容耦合$U_{\rm eff}$，该耦合与所研究的体系的极化能位移$E_p$成正比。讨论了不同参数下的平衡谱函数。在声子频率$\w_0$的倍数处的附加声子峰对应于差分电导的附加最大值。然而，非平衡效应导致对称结和隧道态结之间的显著偏差。本文用一个简单的框架，即(i)极化能级位移和（ii）有效电荷转移尺度$\Gamma_{\rm eff}$的组合，讨论了Franck-Condon封锁的标志——电子-声子耦合增加对非对称结电流的抑制。
We use the recently proposed scattering states numerical renormalization group (SNRG) approach to calculate $I(V)$ and the differential conductance through a single molecular level coupled to a local molecular phonon. We also discuss the equilibrium physics of the model and demonstrate that the low-energy Hamiltonian is given by an effective interacting resonant level model. From the NRG level flow, we directly extract the effective charge transfer scale $\Gamma_{\rm eff}$ and the dynamically induced capacitive coupling $U_{\rm eff}$ between the molecular level and the lead electrons which turns out to be proportional to the polaronic energy shift $E_p$ for the regimes investigated here. The equilibrium spectral functions for the different parameter regimes are discussed. The additional phonon peaks at multiples of the phonon frequency $\w_0$ correspond to additional maxima in the differential conductance. Non-equilibrium effects, however, lead to significant deviations between a symmetric junction and a junction in the tunnel regime. The suppression of the current for asymmetric junctions with increasing electron-phonon coupling, the hallmark of the Franck-Condon blockade, is discussed with a simple framework of a combination of (i) polaronic level shifts and (ii) the effective charge transfer scale $\Gamma_{\rm eff}$.