Numerical renormalization group approach to a quartet quantum-dot array connected to reservoirs: Gate-voltage dependence of the conductance
Numerical renormalization group approach to a quartet quantum-dot array connected to reservoirs: Gate-voltage dependence of the conductance
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DOI：
10.1103/physrevb.73.125108
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发表时间：
2005-11
影响因子：
3.7
通讯作者：
Y. Nisikawa;A. Oguri
中科院分区：
文献类型：
--
作者：
Y. Nisikawa;A. Oguri
利用数值重整化群（NRG）方法，结合与两条非相互作用引线相连的四格点哈伯德模型，对四重态量子点阵列的基态性质进行了研究。具体而言，我们从多体相移计算量子点中的电导和局域电荷，而多体相移可从NRG的不动点本征值推导得出。作为与栅极电压相对应的格点能\(\epsilon_d\)的函数，电导交替呈现出宽峰和宽谷。同时，由于较大的库仑相互作用\(U\)，四个量子点中的电子总数\(N_{\mathrm{el}}\)呈现出量子化的阶梯行为。在\(N_{\mathrm{el}}\)为奇数时出现的幺正极限电导平台是由近藤效应引起的。在\(N_{\mathrm{el}}\)为偶数时出现电导谷，且在半填充时其宽度显著增大。这可被视为一种在小系统中体现的莫特 - 哈伯德绝缘行为。对于链与引线之间较大的杂化强度\(\Gamma\)，这些平台和谷的结构会变弱。我们还讨论了连接到四条引线的阵列的并联电导。
The ground-state properties of quartet quantum-dot arrays are studied using the numerical renormalization group (NRG) method with a four-site Hubbard model connected to two noninteracting leads. Specifically, we calculate the conductance and local charge in the dots from the many-body phase shifts, which can be deduced from the fixed-point eigenvalues of NRG. As a function of the on-site energy ${ϵ}_{d}$ which corresponds to the gate voltage, the conductance shows alternatively wide peaks and valleys. Simultaneously, the total number of electrons ${N}_{\mathrm{el}}$ in the four dots shows a quantized staircase behavior due to a large Coulomb interaction $U$. The conductance plateaus of the unitary limit emerging for odd ${N}_{\mathrm{el}}$ are caused by the Kondo effect. The valleys of the conductance emerge for even ${N}_{\mathrm{el}}$, and their width becomes substantially large at half-filling. It can be regarded as a kind of the Mott-Hubbard insulating behavior manifesting in a small system. These structures of the plateaus and valleys become weak for large values of the hybridization strength $\ensuremath{\Gamma}$ between the chain and leads. We also discuss the parallel conductance for the array connected to four leads.