论文标题
在低温下，巨型热电器和功率因数在魔法角度扭曲的双层石墨烯
Giant thermopower and power factor in magic angle twisted bilayer graphene at low temperature
论文作者
论文摘要
理论上在扭曲的双层石墨烯（TBLG）中研究了平面内的声子热电器$ s^g $，扩散热电器$ s^d $和功率因数$ pf $，作为扭曲角度$θ$，温度$ t $ $ t $和电子密度$ n_s $ n_s $ N_S $在低$ T $ T $ T $（1-20 K）的函数。由于$θ$接近魔法$θ_m$，因此发现$ s^g $和$ s^d $强烈增强，这表现出了对Moire Flat Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band Band band Band age $θ_m$近$ $ $ $ $ $ $ $ $的极大抑制。这种增强功能随着$θ$和$ t $的增加而降低。在Bloch-Gruneisen（BG）制度中，发现$ s^g \ sim {ν_f}^{* -2} $，$ t^3 $和$ {n_s}^{ - 1/2} $。随着$ t $的增加，$ s^g \ sim t^δ$中的指数$δ$从3变为零，最大$ s^g $值为$ \ sim $ \ sim $ 10 mv/k $ \ sim $ 20 k。对于低（高）温度区域的较小$ n_s $，$ s^g $更大（较小）。另一方面，$ s^d $，由Mott公式统治，$ \ sim {ν_f}^{* -1} $，$ t $和$ {n_s}^{ - 1/2} $和$ s^d << s^d << s^d << s^g $ for $ t> sim $ t> sim $ 2k。因此，讨论了巨大的功绩。与TBLG中测量的平面外热电器相比，我们的结果是定性的。
The in-plane phonon-drag thermopower $S^g$, diffusion thermopower $S^d$ and the power factor $PF$ are theoretically investigated in twisted bilayer graphene (tBLG) as a function of twist angle $θ$, temperature $T$ and electron density $n_s$ in the region of low $T$ (1-20 K). As $θ$ approaches magic angle $θ_m$, the $S^g$ and $S^d$ are found to be strongly enhanced, which is manifestation of great suppression of Fermi velocity ${ν_F}^*$ of electrons in moire flat band near $θ_m$. This enhancement decreases with increasing $θ$ and $T$. In the Bloch- Gruneisen (BG) regime, it is found that $S^g \sim {ν_F}^{* -2}$, $T^3$ and ${n_s}^{-1/2}$. As $T$ increases, the exponent $δ$ in $S^g \sim T^δ$, changes from 3 to nearly zero and a maximum $S^g$ value of $\sim$ 10 mV/K at $\sim$ 20 K is estimated. $S^g$ is larger (smaller) for smaller $n_s$ in low (high) temperature region. On the other hand, $S^d$, taken to be governed by Mott formula, $\sim {ν_F}^{* -1}$, $T$ and ${n_s}^{-1/2}$ and $S^d<<S^g$ for $T > \sim$ 2 K. The power factor $PF$ is also found to be strongly $θ$ dependent and very much enhanced. Consequently, possibility of a giant figure of merit is discussed.In tBLG, $θ$ acts as a strong tuning parameter of both $S^g$ and $S^d$ and $PF$ in addition to $T$ and $n_s$. Our results are qualitatively compared with the measured out-of-plane thermopower in tBLG.
