Jožef Stefan Institute, Ljubljana, Slovenia.
Phys Rev Lett. 2012 Feb 10;108(6):066602. doi: 10.1103/PhysRevLett.108.066602. Epub 2012 Feb 8.
We resolve the controversy regarding the ground state of the parallel double quantum dot system near half filling. The numerical renormalization group predicts an underscreened Kondo state with residual spin-1/2 magnetic moment, ln2 residual impurity entropy, and unitary conductance, while the Bethe ansatz solution predicts a fully screened impurity, regular Fermi-liquid ground state, and zero conductance. We calculate the impurity entropy of the system as a function of the temperature using the hybridization-expansion continuous-time quantum Monte Carlo technique, which is a numerically exact stochastic method, and find excellent agreement with the numerical renormalization group results. We show that the origin of the unconventional behavior in this model is the odd-symmetry "dark state" on the dots.
我们解决了在接近半满状态下平行双量子点系统基态的争议。数值重整化群预测存在欠屏蔽的近藤态，具有剩余的自旋 1/2 磁矩、ln2 剩余杂质熵和单位电导，而 Bethe 假设解则预测完全屏蔽的杂质、正则费米液体基态和零电导。我们使用杂交扩展连续时间量子蒙特卡罗技术（一种数值精确的随机方法）计算了系统的杂质熵作为温度的函数，并与数值重整化群结果吻合得非常好。我们表明，该模型中非常规行为的起源是点上的奇对称“暗态”。
