论文标题
石墨烯磁盘中亚果盘电荷传输的理论
Theory of the sub-Sharvin charge transport in graphene disks
论文作者
论文摘要
Ballistic graphene samples in a multimode regime show the sub-Sharvin charge transport, characterized by the conductance reduced by a factor of $π/4$ comparing to standard Sharvin contacts in two-dimensional electron gas, and the shot-noise power enhanced up to $F\approx{}1/8$ (with $F$ the Fano factor) [Phys.修订版B 104，165413（2021）]。在这里，我们考虑石墨烯中的磁盘形（Corbino）设置，内部半径为$ r_1 $和外部半径$ r_2 $，发现任何$ r_1 <r_2 $的多模电导量略有增强，达到$（4 \！ - ！ - \！π）\！在相同的限制下，降低了FANO因子，接近$（9π-28）/（12-3π）\ ot ot {} 0.1065 <1/8 $。任何$ r_1/r_2 $比率的封闭形式的近似表达式是衍生出来的，假设dirac费米子在非对称双屏障上的不一致散射，并与模式匹配方法相比的确切数值结果进行了比较。 sub-sharvin值在窄盘限制$ r_1/r_2 \ rightarrow {} 1 $中恢复。对于实验可访问的半径比$ 0.5 \ leqslant {} r_1/r_1/r_2 \ leqslant {} 0.8 $，电导率和fano因子都与$ r_1 \ ll {} r_2 $ limip的预测值相距甚远，但仍与标准的sharvin sharvin sharvin特征差异。研究了从矩形到抛物线形状调整静电势势垒时的系统行为，并研究了从sharvin到标准Sharvin运输方式的交叉。还讨论了对磁盘有限部分的含义。
Ballistic graphene samples in a multimode regime show the sub-Sharvin charge transport, characterized by the conductance reduced by a factor of $π/4$ comparing to standard Sharvin contacts in two-dimensional electron gas, and the shot-noise power enhanced up to $F\approx{}1/8$ (with $F$ the Fano factor) [Phys. Rev. B 104, 165413 (2021)]. Here we consider the disk-shaped (Corbino) setup in graphene, with inner radius $r_1$ and outer radius $r_2$, finding that the multimode conductance is slightly enhanced for any $r_1<r_2$, reaching $(4\!-\!π)\approx{}0.8684$ of the Sharvin value for $r_1\ll{}r_2$. At the same limit, the Fano factor is reduced, approaching $(9π-28)/(12-3π)\approx{}0.1065<1/8$. Closed-form approximating expressions for any $r_1/r_2$ ratio are derived supposing incoherent scattering of Dirac fermions on asymmetric double barrier and compared with exact numerical results following from the mode-matching method. Sub-Sharvin values are restored in the narrow-disk limit $r_1/r_2\rightarrow{}1$. For experimentally-accessible radii ratios $0.5\leqslant{}r_1/r_2\leqslant{}0.8$ both the conductance and the Fano factor are noticeably closer to the values predicted for the $r_1\ll{}r_2$ limit, yet still differ from standard Sharvin transport characteristics. The system behavior upon tuning the electrostatic potential barrier from a rectangular to parabolic shape is studied numerically, and the crossover from the sub-Sharvin to standard Sharvin transport regime is demonstrated. Implications for a finite section of the disk are also discussed.
