复杂量子系统中激子扩散长度：无序和环境涨落对量子增强超转移的影响
Excitonic diffusion length in complex quantum systems: The effects of disorder and environmental fluctuations on symmetry-enhanced supertransfer
摘要：
$n$发色团聚集体之间的对称耦合使激子的转移速率增加了一个因子$n^2$，这是一种称为“超转移”的量子力学现象。“在这项工作中，我们证明了几何对称性引起的超转移效应如何可以增强激子扩散长度的一个因素$n$沿圆柱对称结构，由发色团环阵列，并沿螺旋阵列。我们分析了封闭系统动力学和开放量子动力学，建模相结合的随机玻色子浴与静态无序。在封闭系统的情况下，我们使用系统的对称性在一个短时间的近似，以获得一个封闭的解析表达式的扩散长度，明确揭示了超传输的贡献。当受到无序，我们表明，超转移可以提高激子扩散长度为小的障碍和特征的交叉从相干到非相干运动。由于模型的准一维性质，无序最终使激子局域化，减少但不破坏超转移的影响。当失相效应被包括在内，我们研究的扩散与时间和数量的发色团的标度，并观察到，从一个连贯的，弹道制度的过渡到一个不连贯的，随机行走制度发生在同一点的变化从超转移到经典标度。
英文摘要：
Symmetric couplings among aggregates of $n$ chromophores increase the transfer rate of excitons by a factor $n^2$, a quantum mechanical phenomenon called "supertransfer." In this work we demonstrate how supertransfer effects induced by geometrical symmetries can enhance the exciton diffusion length by a factor $n$ along cylindrically symmetric structures, consisting of arrays of rings of chromophores, and along spiral arrays. We analyse both closed system dynamics and open quantum dynamics, modelled by combining a random bosonic bath with static disorder. In the closed system case, we use the symmetries of the system within a short-time approximation to obtain a closed analytical expression for the diffusion length that explicitly reveals the supertransfer contribution. When subject to disorder, we show that supertransfer can enhance excitonic diffusion lengths for small disorders and characterize the crossover from coherent to incoherent motion. Owing to the quasi-1D nature of the model, disorder ultimately localizes the excitons, diminishing but not destroying the effects of supertransfer. When dephasing effects are included, we study the scaling of diffusion with both time and number of chromophores and observe that the transition from a coherent, ballistic regime to an incoherent, random-walk regime occurs at the same point as the change from supertransfer to classical scaling.
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