The electric conductivity of Dirac electrons in the organic conductor α-(BEDT-TTF)₂I₃ [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene] under pressure has been examined using a two-dimensional tight-binding (TB) model with both impurity and electron–phonon (e–p) scatterings. We study an anomalous temperature dependence of the conductivity, which shows a crossover from σ_x < σ_y at low temperatures [region (I)] to σ_x > σ_y at high temperatures [region (II)]. σ_y and σ_x are diagonal conductivities parallel and perpendicular to a stacking axis of molecules, respectively. The effect of Dirac cone tilting is dominant in region (I), whereas the anisotropy of the velocity of the Dirac cone is dominant in region (II). Such behavior is further examined by calculating the deviation of principal axes due to the off-diagonal conductivity σ_xy and a nearly constant conductivity at high temperatures due to the e–p scattering, which is the extension of the previous result of the simple two-band model [Phys. Rev. B 98, 161205 (2018)]. The relevance to experiments of organic conductors is discussed.

中文翻译：

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压力下有机导体中二维狄拉克电子的反常电导率

使用二维紧密结合（TB）模型检查了有机导体中α-（BEDT-TTF）₂ I ₃ [BEDT-TTF =双（亚乙基二硫代）四硫富瓦烯]中狄拉克电子的电导率杂质和电子-声子（e-p）散射。我们研究了导电性的异常的温度依赖性，其示出了从一个交叉σ _X < σ _ÿ在低温下[区域（I）]，以σ _X > σ _ý在高温下[区域（II）]。σ _ÿ和σ _X分别是平行和垂直于分子堆叠轴的对角线电导率。狄拉克锥锥倾斜的影响在区域（I）中占主导地位，而狄拉克锥锥速度的各向异性在区域（II）中占主导地位。通过计算主轴的偏差由于被进一步检验这种行为非对角线电导率σ_的xy和在高温下，由于电子-对散射，这是简单的双的先前结果的延伸几乎恒定的电导率带模型[Phys。版本B 98，161205（2018）]。讨论了与有机导体实验的相关性。