Ambipolar transport is a commonly occurring theme in semimetals and semiconductors. Here we present an analytical formulation of the conductivity for a two-band system. Electron and hole carrier densities and their respective conductivities are mapped into a two-dimensional unit-less phase space. Provided that one of the carrier densities is known, the dimensionless phase space can be probed through magnetoresistance measurements. This formulation of the two-band model for conductivity is applied to magnetoresistance experiments on Ca₃Ru₂O₇. While previous such measurements focused on the low-temperature limit, we cover a broad temperature range and find negative magnetoresistance in an intermediate interval below the electronic transition at 48 K. The low-temperature magnetoresistance in Ca₃Ru₂O₇ is consistent with a two-band structure. However, the model fails to describe the full temperature and magnetic field dependence. Negative magnetoresistance found in an intermediate temperature range is, for example, not captured by this model. We thus conclude that the electronic and magnetic structure in this intermediate temperature range render the system beyond the most simple two-band model.

中文翻译：

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双载子磁阻：在Ca3Ru2O7中的应用

双极传输是半金属和半导体中经常发生的主题。在这里，我们介绍了两频带系统的电导率的解析公式。电子和空穴载流子密度及其各自的电导率被映射到二维无单元相空间中。如果已知载流子密度之一，则可以通过磁阻测量来探测无量纲的相空间。电导率的两带模型的这种公式可用于Ca ₃ Ru ₂ O _7的磁阻实验。虽然以前的这样的测量集中在低温限制，我们覆盖宽的温度范围内，发现负磁阻在电子跃迁低于48 K的低温磁致电阻在钙的中间间隔₃的Ru ₂ ö ₇是具有一致两频结构。但是，该模型无法描述完整的温度和磁场依赖性。例如，该模型未捕获在中间温度范围内发现的负磁阻。因此，我们得出的结论是，在此中间温度范围内的电子和磁性结构使系统超出了最简单的两波段模型。