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首页> 外文期刊>Physical review >Pseudodiffusive conductance, quantum-limited shot noise, and Landau-level hierarchy in a biased graphene bilayer
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Pseudodiffusive conductance, quantum-limited shot noise, and Landau-level hierarchy in a biased graphene bilayer

机译：偏置石墨烯双层中的伪扩散电导，量子限制散粒噪声和Landau级层次

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We discuss, by means of mode-matching analysis for the Dirac equation, how splittings of the Landau-level (LL) degeneracies associated with spin, valley, and layer degrees of freedom affect the ballistic conductance of graphene bilayer. The results show that for wide samples (W » L) the Landauer-Buettiker conductance reaches the maximum G (≌) se~2/(πh) × W/L at the resonance via each LL, with the prefactor varying from s = 8 if all three degeneracies are preserved, to s = 1 if all the degeneracies are split. In the absence of bias between the layers, the degeneracies associated with spin and layer degrees of freedom may be split by manipulating the doping and magnetic field; the conductance at the zeroth LL is twice as large, while the conductance at any other LL equals to the corresponding conductance of graphene monolayer. The presence of bias potential allows one also to split the valley degeneracy. Our results show that the charge transfer at each LL has pseudodiffusive character, with the second and third cumulant quantified by F = 1/3 and R = 1/15 (respectively). In case the electrochemical potential is allowed to slowly fluctuate in a finite vicinity of LL, the resulting charge-transfer characteristics are still quantum limited, with F (≌) 0.7 and R (≌) 0.5 in the limit of large fluctuations. Analogously, the above values of F and R are predicted to be approached in the limit of high source-drain voltage difference applied. The possible effects of indirect interlayer hopping integrals are also briefly discussed.
机译：我们通过对Dirac方程进行模式匹配分析来讨论与自旋，谷和层自由度相关的Landau级（LL）简并的分裂如何影响石墨烯双层的弹道电导。结果表明，对于宽样本（W»L），Landauer-Buettiker电导在每个LL的共振点处达到最大G（≌）se〜2 /（πh）×W / L，前因子从s = 8如果保留了所有三个简并性，则如果拆分了所有简并性，则s = 1。在各层之间不存在偏压的情况下，可以通过控制掺杂和磁场来分裂与自旋和层自由度相关的简并性。第零个LL处的电导是其两倍，而其他任何LL处的电导都等于相应的石墨烯单层电导。偏置电位的存在也可以使谷的简并性分裂。我们的结果表明，每个LL处的电荷转移具有伪扩散特性，第二和第三累积量分别由F = 1/3和R = 1/15量化。如果允许电化学电势在LL的有限范围内缓慢波动，则所得的电荷转移特性仍受量子限制，其中F（≌）0.7和R（≌）0.5受较大波动的限制。类似地，预计在施加的高源漏电压差的极限内，将接近F和R的上述值。还简要讨论了间接层间跳跃积分的可能影响。

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