Bipolaron mechanism for organic magnetoresistance
Bipolaron mechanism for organic magnetoresistance
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DOI：
10.1103/physrevlett.99.216801
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发表时间：
2007-11-23
影响因子：
8.6
通讯作者：
Wohlgenannt, M.
中科院分区：
文献类型：
--
作者：
Bobbert, P. A.;Nguyen, T. D.;Wohlgenannt, M.
我们基于极化子的跳跃和双极化子的形成，在氢核的随机超精细场以及外部磁场存在的情况下，为最近在无序π共轭材料中发现的磁阻提出了一种机制。在一个简单的模型中，我们描述了双极化子密度对磁场的依赖性。包括在位库仑排斥和长程库仑排斥的蒙特卡罗模拟表明了这如何导致正磁阻和负磁阻。根据双极化子形成或解离与跳跃速率之间的分支比，可以得到两种与实验非常吻合的不同线形。
We present a mechanism for the recently discovered magnetoresistance in disordered pi-conjugated materials, based on hopping of polarons and bipolaron formation, in the presence of the random hyperfine fields of the hydrogen nuclei and an external magnetic field. Within a simple model we describe the magnetic field dependence of the bipolaron density. Monte Carlo simulations including on-site and longer-range Coulomb repulsion show how this leads to positive and negative magnetoresistance. Depending on the branching ratio between bipolaron formation or dissociation and hopping rates, two different line shapes in excellent agreement with experiment are obtained.