A single confined spin interacting with a solid-state environment has emerged as one of the fundamental paradigms of mesoscopic physics. In contrast to standard quantum optical systems, decoherence that stems from these interactions can in general not be treated using the Born-Markov approximation at low temperatures. Here we study the non-equilibrium dynamics of a single-spin in a semiconductor quantum dot adjacent to a fermionic reservoir and show how the dynamics can be revealed in detail in an optical absorption experiment. We show that the highly asymmetrical optical absorption lineshape of the resulting Kondo exciton consists of three distinct frequency domains, corresponding to short, intermediate and long times after the initial excitation, which are in turn described by the three fixed points of the single-impurity Anderson Hamiltonian. The zero-temperature power-law singularity dominating the lineshape is linked to dynamically generated Kondo correlations in the photo-excited state. We show that this power-law singularity is tunable with gate voltage and magnetic field, and universal.
Exact description of fermionic reservoirs via purified damped ancillary fermions
Inner Mongolia University（内蒙古大学）；RIKEN Center for Quantum Computing (RQC)（理研量子计算中心）；Graduate School of China Academy of Engineering Physics（中国工程物理研究院研究生院）
Efficient low temperature simulations for fermionic reservoirs with the hierarchical equations of motion method: Application to the Anderson impurity model
Fermionic superoperators for zero-temperature non-linear transport: real-time perturbation theory and renormalization group for Anderson quantum dots
在约化密度算符动力学方程的框架下，利用实时重整化群（RT-RG）方法研究了零温下强相互作用Anderson量子点的输运.我们进一步发展了一般的有限温度实时传输形式主义，通过引入场超算子，遵守费米统计。这种在刘维尔-福克空间中的直接二次量子化极大地简化了在安德森模型对称变换下不可约变换的算子和超算子的构造。费米子场超算符自然地产生于整个系统的单价（费米子宇称）超选择规则。表达在这些领域的超算子，因果结构的微扰理论的有效时间演化超算子内核变得明确。因果结构还意味着存在精确Liouvillian的费米子宇称保护本征向量，解释了最近报道的关于绝热驱动的结果[Phys. Rev. B 85，075301（2012）]，并将其推广到隧道耦合中的任意阶。此外，在WBL中，因果表示指数地减少了时间演化内核的图的数量。我们在有限电压和磁场下进行了完整的2回路RG分析，同时系统地考虑了对量子点和水库频率的依赖性。使用第二量子化的刘维尔空间和对称性的限制，我们得到一个有效的数值解的分析RT-RG方程，我们广泛研究的模型参数空间，不包括近藤政权。合并重整化效应的结果在非弹性共隧穿峰的增强。此外，我们发现隧道诱导的非线性的稳定性图在有限的电压，无论是在SET和ICT制度。
