Equivalence of Effective Medium and Random Resistor Network models for disorder-induced unsaturating linear magnetoresistance
Equivalence of Effective Medium and Random Resistor Network models for disorder-induced unsaturating linear magnetoresistance
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DOI：
10.1103/physrevb.96.224203
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发表时间：
2017-03
影响因子：
3.7
通讯作者：
Navneeth Ramakrishnan;Y. Lai;S. Lara;M. Parish;S. Adam
中科院分区：
文献类型：
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作者：
Navneeth Ramakrishnan;Y. Lai;S. Lara;M. Parish;S. Adam
在高垂直磁场下的线性不饱和磁电阻，以及在低磁场下的二次正磁电阻，已经在许多不同的实验材料中被发现，从硫化物银和InSb薄膜到石墨烯和狄拉克半金属等拓扑材料。在文献中，两种截然不同的理论方法被用来解释这种由样品无序引起的经典磁电阻。现象学随机电阻网络模型构建了一个四端电阻的网格，每个电阻具有不同的随机电阻。有效介质理论模型设想了一个平滑变化的无序势，导致局部电导率的连续变化。本文用数值方法证明了两种模型都属于同一个普适性类，并且随机电阻网络的一个限制类实际上等价于有效介质理论。这两种模型也与各种材料的实验结果很好地吻合。此外，我们表明，在这两种情况下，一个参数，即载流子密度波动与平均载流子密度的比值，完全决定了磁阻分布。
A linear unsaturating magnetoresistance at high perpendicular magnetic fields, together with a quadratic positive magnetoresistance at low fields, has been seen in many different experimental materials, ranging from silver chalcogenides and thin films of InSb to topological materials like graphene and Dirac semimetals. In the literature, two very different theoretical approaches have been used to explain this classical magnetoresistance as a consequence of sample disorder. The phenomenological Random Resistor Network model constructs a grid of four-terminal resistors, each with a varying random resistance. The Effective Medium Theory model imagines a smoothly varying disorder potential that causes a continuous variation of the local conductivity. Here, we demonstrate numerically that both models belong to the same universality class and that a restricted class of the Random Resistor Network is actually equivalent to the Effective Medium Theory. Both models are also in good agreement with experiments on a diverse range of materials. Moreover, we show that in both cases, a single parameter, i.e. the ratio of the fluctuations in the carrier density to the average carrier density, completely determines the magnetoresistance profile.