Recent experiments have reported evidence of dominant electron-hole scattering in the electric conductivity of suspended bilayer graphene near charge neutrality. According to these experiments, plots of the electric conductivity as a function of $\mu /k_{B}T$ (chemical potential scaled with temperature) obtained for different temperatures in the range of $12\mathrm{K}\lesssim T\lesssim 40\mathrm{K}$ collapse on a single curve independent of $T$. In a recent theory, this observation has been taken as an indication that the main subdominant scattering process is not electron impurity but electron-phonon. Here, we demonstrate that the collapse of the data on a single curve can be explained without invoking electron-phonon scattering but assuming that the suspended bilayer graphene is not a truly gapless system and by including the effect of electron-hole puddles in the subdominant charged impurity scattering mechanism. With a gap of $\sim 5\mathrm{meV}$, our theory produces excellent agreement with the observed conductivity over the full reported range of temperatures. These results are based on the hydrodynamic theory of conductivity, which, thus, emerges as a solid foundation for the analysis of experiments and the estimation of the band gap in multiband systems.

中文翻译：

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双层石墨烯中电导率的温度崩溃

最近的实验报道了在电荷中性附近悬浮的双层石墨烯的电导率中主要的电子-空穴散射的证据。根据这些实验，电导率与$\mu /{ķ}_{乙}Ť$ 在以下温度范围内获得的不同温度（化学势随温度缩放） $12\mathrm{ķ}\lesssim Ť\lesssim 40\mathrm{ķ}$ 独立于一条曲线而独立于 $Ť$。在最近的理论中，该观察已被视为主要的主要散射过程不是电子杂质而是电子-声子。在这里，我们证明了在不调用电子-声子散射但假设悬浮的双层石墨烯不是真正的无间隙体系并且通过在主要电荷中包含电子空穴坑的影响的情况下，可以解释单条曲线上数据的崩溃杂质扩散机制。与之间的差距$〜5\mathrm{病毒}$，我们的理论与在整个报告的温度范围内观察到的电导率有着极好的一致性。这些结果基于电导率的流体力学理论，因此为分析实验和估计多频带系统中的带隙奠定了坚实的基础。