Minarelli Emma L, Rigo Jonas B, Mitchell Andrew K
School of Physics, University College Dublin, Dublin 4, Ireland.
Centre for Quantum Engineering, Science, and Technology, University College Dublin, Dublin 4, Ireland.
Nanomaterials (Basel). 2022 Apr 29;12(9):1513. doi: 10.3390/nano12091513.
Nanoelectronic quantum dot devices exploiting the charge-Kondo paradigm have been established as versatile and accurate analogue quantum simulators of fundamental quantum impurity models. In particular, hybrid metal-semiconductor dots connected to two metallic leads realize the two-channel Kondo (2CK) model, in which Kondo screening of the dot charge pseudospin is frustrated. In this article, a two-channel charge-Kondo device made instead from graphene components is considered, realizing a pseudogapped version of the 2CK model. The model is solved using Wilson's Numerical Renormalization Group method, uncovering a rich phase diagram as a function of dot-lead coupling strength, channel asymmetry, and potential scattering. The complex physics of this system is explored through its thermodynamic properties, scattering T-matrix, and experimentally measurable conductance. The strong coupling pseudogap Kondo phase is found to persist in the channel-asymmetric two-channel context, while in the channel-symmetric case, frustration results in a novel quantum phase transition. Remarkably, despite the vanishing density of states in the graphene leads at low energies, a linear conductance is found at zero temperature at the frustrated critical point, which is of a non-Fermi liquid type. Our results suggest that the graphene charge-Kondo platform offers a unique possibility to access multichannel pseudogap Kondo physics.
利用电荷近藤范式的纳米电子量子点器件已被确立为基本量子杂质模型的通用且精确的模拟量子模拟器。特别是，连接到两个金属引线的混合金属 - 半导体点实现了双通道近藤（2CK）模型，其中点电荷赝自旋的近藤屏蔽受到阻碍。在本文中，考虑了一种由石墨烯组件制成的双通道电荷近藤器件，实现了2CK模型的赝能隙版本。使用威尔逊数值重整化群方法求解该模型，揭示了作为点 - 引线耦合强度、通道不对称性和势散射函数的丰富相图。通过其热力学性质、散射T矩阵和实验可测量的电导来探索该系统的复杂物理。发现强耦合赝能隙近藤相在通道不对称的双通道情况下持续存在，而在通道对称的情况下，阻碍导致了一种新型量子相变。值得注意的是，尽管石墨烯引线在低能量下态密度消失，但在受挫临界点的零温度下发现了线性电导，这是非费米液体类型的。我们的结果表明，石墨烯电荷近藤平台为研究多通道赝能隙近藤物理提供了独特的可能性。
