arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1308.0983cond-mat.mes-hallcond-mat.str-el
收藏

高偏压下Anderson杂质的精确相互作用格林函数

Exact interacting Green's function for the Anderson impurity at high bias voltages

Akira Oguri, Rui Sakano

摘要:

我们描述了在非平衡稳态中,一个单独的安德森杂质与两个非相互作用的铅原子相连时的一些精确的高能性质。在高偏置电压的限制下,以及在高温限制下的热平衡,该模型可以被映射到一个有效的非厄米哈密顿量的两个网站,这对应于原来的杂质和它的图像,被定义在一个双重的希尔伯特空间被称为刘维尔-福克空间。为此,我们提供了一个启发式的推导使用的路径积分表示的Keldysh轮廓和热场论,其中沿向后轮廓的时间演化复制对应于图像的额外的自由度。我们发现有效哈密顿量也可以用电荷和电流来表示。由此可以推断,在高偏压极限下,电荷和电流波动的动态极化率变得与库仑排斥U无关。格林函数的运动方程与另外两个高阶关联函数构成一个封闭系统。从三个耦合方程得到的精确解扩展了原子极限解,使得自能正确地捕获了高能量下弛豫过程引起的虚部。上、下哈伯德能级的谱权重敏感地依赖于左右导联隧穿耦合的不对称性。

英文摘要:

We describe some exact high-energy properties of a single Anderson impurity connected to two noninteracting leads in a nonequilibrium steady state. In the limit of high bias voltages, and also in the high-temperature limit at thermal equilibrium, the model can be mapped on to an effective non-Hermitian Hamiltonian consisting of two sites, which correspond to the original impurity and its image that is defined in a doubled Hilbert space referred to as Liouville-Fock space. For this, we provide a heuristic derivation using a path-integral representation of the Keldysh contour and the thermal field theory, in which the time evolution along the backward contour is replicated by extra degrees of freedom corresponding to the image. We find that the effective Hamiltonian can also be expressed in terms of charges and currents. From this, it can be deduced that the dynamic susceptibilities for the charges and the current fluctuations become independent of the Coulomb repulsion U in the high bias limit. Furthermore, the equation of motions for the Green's function and two other higher-order correlation functions constitute a closed system. The exact solution obtained from the three coupled equations extends the atomic-limit solution such that the self-energy correctly captures the imaginary part caused by the relaxation processes at high energies. The spectral weights of the upper and lower Hubbard levels depend sensitively on the asymmetry in the tunneling couplings to the left and right leads.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑