Tunneling conductance through two quantum dots, which are connected in seriesto left and right leads, is calculated by using the numerical renormalizationgroup method. As the hopping between the dots increases from very small value,the following states continuously appear; (i) Kondo singlet state of each dotwith its adjacent-site lead, (ii) singlet state between the local spins on thedots, and (iii) double occupancy in the bonding orbital of the two dots. Theconductance shows peaks at the transition regions between these states.Especially, the peak at the boundary between (i) and (ii) has the unitaritylimit value of $2e^{2}/h$ because of coherent connection through thelead-dot-dot-lead. For the strongly correlated cases, the characteristic energyscale of the coherent peak shows anomalous decrease relating to the quantumcritical transition known for the two-impurity Kondo effect. The two dotssystems give the new realization of the two-impurity Kondo problem.
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机译：通过使用数值重归一化群方法，计算通过串联连接到左右引线的两个量子点的隧道电导。当点之间的跳变从非常小的值开始增加时，以下状态不断出现； （i）每个点的近藤单线态及其相邻位点的铅，（ii）点上局部自旋之间的单线态，以及（iii）两个点的键合轨道中的双重占据。该电导在这些状态之间的过渡区域显示出峰值。特别是，由于通过引线-点-点的相干连接，（i）和（ii）之间的边界处的峰的统一极限值为$ 2e ^ {2} / h $。 -铅。对于高度相关的情况，相干峰的特征能级显示出异常减少，这与已知的两个杂质近藤效应的量子临界跃迁有关。两个点系统为两杂质近藤问题提供了新的认识。
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