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Dynamical properties of a nonequilibrium quantum dot close to a dissipative quantum phase transition

机译：接近耗散量子相变的非平衡量子点的动力学性质

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摘要

The dynamical decoherence rate and charge susceptibility of a nonequilibrium quantum dot close to a dissipative quantum phase transition are calculated. The setup concerns a resonance-level quantum dot coupled to two spinless fermionic baths with a finite bias voltage and an ohmic bosonic bath representing a dissipative environment. The system is equivalent to an anisotropic Kondo model. As dissipation strength increases, the system at zero temperature and zero bias exhibits a quantum phase transition of the Kosterlitz-Thouless (KT) type between a conducting delocalized phase and an insulating localized phase. Within the nonequilibrium frequency-dependent renormalization group (RG) approach, the finite bias crossover in dynamical decoherence rate and charge susceptibility close to the transition are addressed. The dynamical decoherence rate is found to increase with increasing frequency. In the delocalized phase, it shows a singularity at frequencies equal to positive or negative bias voltage. As the system cross overs to the localized phase, the decoherence rate at low frequencies gets progressively smaller and the singular feature is gradually smeared out, leading to a single linear frequency dependence. The dynamical charge susceptibility at low frequencies shows a dip-to-peak crossover across the transition. Relevance of these results to the experiments is discussed.
机译：计算了接近耗散量子相变的非平衡量子点的动态退相干率和电荷敏感性。该装置涉及一个谐振级量子点，该量子点耦合到两个具有有限偏置电压的无旋铁氧体浴池和一个代表耗散环境的欧姆性硼离子浴池。该系统等效于各向异性的近藤模型。随着耗散强度的增加，处于零温度和零偏压的系统在导电离域相和绝缘局域相之间呈现出Kosterlitz-Thouless（KT）类型的量子相变。在非平衡频率相关的重归一化组（RG）方法中，解决了动态去相干速率和接近过渡的电荷磁化率的有限偏差交叉问题。发现动态退相干率随频率增加而增加。在离域阶段，它在等于正或负偏置电压的频率下显示出奇异性。随着系统过渡到局部相位，低频的退相干率逐渐变小，奇异特征逐渐被抹去，从而导致了单线性频率依赖性。低频处的动态电荷磁化率显示出整个跃迁的峰谷交叉。讨论了这些结果与实验的相关性。

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  • 来源
    《Physical review》 |2011年第11期|p.115308.1-115308.8|共8页
  • 作者

    Chung-Hou Chung;

  • 作者单位

    Electrophysics Department, National Chiao-Tung University, HsinChu, Taiwan 300, Republic of China Departments of Physics and Applied Physics, Yale University, New Haven, Connecticut 06511, USA;

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  • 正文语种 eng
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  • 关键词

    scattering mechanisms and kondo effect;

    机译：散射机制和近藤效应;

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