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首页> 外文期刊>Physical review.B.Condensed matter and materials physics >Thermal transport in compensated semimetals: Effect of electron-electron scattering on Lorenz ratio
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Thermal transport in compensated semimetals: Effect of electron-electron scattering on Lorenz ratio

机译：补偿半岩的热输送：电子 - 电子散射对洛伦茨比的影响

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It is well known that the electronic thermal conductivity of clean compensated semimetals can be greatly enhanced over the electric conductivity by the availability of an ambipolar mechanism of conduction, whereby electrons and holes flow in the same direction experiencing negligible Coulomb scattering as well as negligible impurity scattering. This enhancement-resulting in a breakdown of the Wiedemann-Franz law with an anomalously large Lorenz ratio-has been recently observed in two-dimensional monolayer and bilayer graphene near the charge neutrality point. In contrast to this, three-dimensional compensated semimetals such as WP_2 and Sb are typically found to show a reduced Lorenz ratio. We investigate the reasons for this difference, focusing on the low-temperature regime where the electron-electron scattering is expected to dominate over other scattering mechanisms. We show that the different regimes of Fermi statistics (nondegenerate electron-hole liquid in graphene versus degenerate electron-hole liquid in compensated semimetals) are not sufficient to explain the reduction of the Lorenz ratio in the latter. We propose that the solution of the puzzle lies in the large separation of electron and hole pockets in momentum space, which allows compensated semimetals to sustain sizable regions of electron-hole accumulation near the contacts. These accumulations suppress the ambipolar conduction mechanism and effectively split the system into two independent electron and hole conductors. We present a quantitative theory of the crossover from ambipolar to unipolar conduction as a function of the size of the electron-hole accumulation regions, and show that it naturally leads to a sample-size-dependent thermal conductivity.
机译：众所周知，通过可用的传导机理，可以大大提高清洁补偿半岩的电子导热率，从导电机构的可用性的情况下，在相同的方向上流动的电子和孔流动忽略不计的库仑散射以及可忽略不计的杂质散射。这种增强导致Wiedemann-Franz定律的崩溃，最近在二维单层和双层石墨烯附近观察到电荷中性点附近的二维单层和双层石墨烯。与此相反，通常发现诸如WP_2和SB的三维补偿半岩，以显示降低的Lorenz比。我们调查这种差异的原因，重点关注预期电子 - 电子散射的低温制度来定位在其他散射机构上。我们表明FERMI统计（石墨烯中的非值电子 - 空穴液体在补偿半型中的Nondegenere电子 - 空穴液体）的不同制度不足以解释后者中Lorenz比的降低。我们提出了拼图的解决方案在于动量空间中的电子和孔袋的大分离，这允许补偿半定在触点附近维持电子空穴积聚的可相同区域。这些累积抑制了非芯片导通机构，并有效地将系统分成了两个独立的电子和孔导体。我们以电子 - 空穴积聚区域的尺寸的函数向单极传导的分流的定量理论，并表明它自然导致样品尺寸依赖性导热率。

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  • 来源
    《Physical review.B.Condensed matter and materials physics》 |2020年第21期|214304.1-214304.10|共10页
  • 作者

    Mohammad Zarenia; Alessandro Principi; Giovanni Vignale;

  • 作者单位

    Department of Physics and Astronomy University of Missouri Columbia Missouri 65211 USA and School of Physics University of Manchester Oxford Road Manchester M13 9PL United Kingdom;

    Department of Physics and Astronomy University of Missouri Columbia Missouri 65211 USA and School of Physics University of Manchester Oxford Road Manchester M13 9PL United Kingdom;

    Department of Physics and Astronomy University of Missouri Columbia Missouri 65211 USA and School of Physics University of Manchester Oxford Road Manchester M13 9PL United Kingdom;

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