Exploring the anisotropic Kondo model in and out of equilibrium with alkaline-earth atoms
Exploring the anisotropic Kondo model in and out of equilibrium with alkaline-earth atoms
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DOI：
10.1103/physrevb.97.155156
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发表时间：
2018-01
影响因子：
3.7
通讯作者：
M'arton Kan'asz-Nagy;Yuto Ashida;T. Shi;C. P. Moca;C. P. Moca;Tatsuhiko N. Ikeda;S. Fölling;J. Cirac;G. Zar'and;E. Demler
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文献类型：
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作者：
M'arton Kan'asz-Nagy;Yuto Ashida;T. Shi;C. P. Moca;C. P. Moca;Tatsuhiko N. Ikeda;S. Fölling;J. Cirac;G. Zar'and;E. Demler
我们提出了一个方案，实现了近藤模型与可调各向异性使用碱土金属原子在一个光学晶格。我们的设置的新功能是Floquet工程的相互作用，使用随时间变化的塞曼位移，可以实现使用状态相关的光学斯塔克位移或磁场。所得到的Kondo模型的性质强烈依赖于铁磁相互作用的各向异性。特别是，易平面耦合引起近藤单态形成，即使微观相互作用都是铁磁的。我们讨论了可以用超冷原子测量的系统的平衡和动力学性质，包括杂质自旋磁化率，杂质自旋弛豫速率，以及杂质和铁磁浴原子之间的平衡和动力学自旋关联。我们使用变分非高斯方法分析系统的非平衡时间演化，这使我们能够探索短时间尺度和长时间尺度上的相干动力学，分别由带宽和近藤单线态形成。在猝灭型实验中，当近藤相互作用突然打开时，我们发现实时动力学显示出交叉，让人想起穷人的重整化群流用于描述平衡系统。对于裸易平面铁磁耦合，这使我们能够遵循近藤屏蔽云的形成，从铁磁到反铁磁行为的动力学交叉。在相图的另一侧，我们的计划使得有可能测量量子修正著名的科林加定律描述的杂质自旋弛豫速率的温度依赖性。我们的论文中讨论的理论结果可以使用目前可用的实验技术进行测量。
We propose a scheme to realize the Kondo model with tunable anisotropy using alkaline-earth atoms in an optical lattice. The new feature of our setup is Floquet engineering of interactions using time-dependent Zeeman shifts, that can be realized either using state-dependent optical Stark shifts or magnetic fields. The properties of the resulting Kondo model strongly depend on the anisotropy of the ferromagnetic interactions. In particular, easy-plane couplings give rise to Kondo singlet formation even though microscopic interactions are all ferromagnetic. We discuss both equilibrium and dynamical properties of the system that can be measured with ultracold atoms, including the impurity spin susceptibility, the impurity spin relaxation rate, as well as the equilibrium and dynamical spin correlations between the impurity and the ferromagnetic bath atoms. We analyze the nonequilibrium time evolution of the system using a variational non-Gaussian approach, which allows us to explore coherent dynamics over both short and long timescales, as set by the bandwidth and the Kondo singlet formation, respectively. In the quench-type experiments, when the Kondo interaction is suddenly switched on, we find that real-time dynamics shows crossovers reminiscent of poor man's renormalization group flow used to describe equilibrium systems. For bare easy-plane ferromagnetic couplings, this allows us to follow the formation of the Kondo screening cloud as the dynamics crosses over from ferromagnetic to antiferromagnetic behavior. On the other side of the phase diagram, our scheme makes it possible to measure quantum corrections to the well-known Korringa law describing the temperature dependence of the impurity spin relaxation rate. Theoretical results discussed in our paper can be measured using currently available experimental techniques.