CLASSICAL AND QUANTUM BALLISTIC-TRANSPORT ANOMALIES IN MICROJUNCTIONS
CLASSICAL AND QUANTUM BALLISTIC-TRANSPORT ANOMALIES IN MICROJUNCTIONS
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DOI：
10.1103/physrevb.44.10637
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发表时间：
1991-11-15
影响因子：
3.7
通讯作者：
STONE, AD
中科院分区：
文献类型：
--
作者：
BARANGER, HU;DIVINCENZO, DP;STONE, AD
我们对二维四端结在弹道区域的磁输运行为进行了量子力学和经典计算。在实验上，这些系统在小场下表现出磁输运异常，抑制(“猝灭”)霍尔电阻，增强弯曲电阻，我们在模型计算中再现了这一点。由于结构是弹道的，结的几何特征的散射是导致异常输运行为的原因。我们研究了几种不同类型的结(包括具有软壁和硬壁的结)，发现它们的霍尔电阻和弯曲电阻对结的几何形状非常敏感。对我们的结果进行分析，得出三个主要结论。(1)在霍尔电阻发生猝灭或反转的所有情况下，或者在零磁场下存在大的弯曲电阻的情况下，注入电子的准直是重要的。准直意味着注入电子的动量分布由于结附近导线的逐渐加宽而向大的平行动量方向加权。(2)由经典计算和量子计算得到的电阻有很大不同。首先，零温下的量子结果与经典结果有很大的不同，因为长路径间的干涉引起了很大的涨落。这种效应被1K数量级的温度抑制，并在其他地方得到了治疗。在这项工作中，我们主要关注通过两种不同的平均过程提取的平均量子行为。经典和量子的结果有很好的定性一致性；然而，我们发现大量的定量差异一直持续到多通道(经典)极限。(3)根据影响霍尔或弯曲阻力的电子轨迹类型对经典结果进行了分析，发现弹道反常是由短轨迹引起的。特别是，我们发现长的“混乱”轨迹在产生这些反常现象时并不重要。这些结论得到了局域输运量的量子计算的支持和说明：电荷密度、电流密度、Wigner分布和Husimi分布。在Wigner和Husimi分布中，注入电子的准直和特定短轨迹的重要性特别明显。
We have performed quantum-mechanical and classical calculations of the magnetotransport behavior of two-dimensional four-terminal junctions in the ballistic regime. Experimentally, these systems exhibit magnetotransport anomalies at small fields, suppression ("quenching") of the Hall resistance, and enhanced bend resistance, which we have reproduced with our model calculations. Because the structures are ballistic, scattering from geometric features of the junction are responsible for the anomalous transport behavior. We study several different kinds of junction (including those with soft and hard walls) and find that their Hall and bend resistances are extremely sensitive to the geometry of the junction. Analysis of our results leads to three major conclusions. (1) In all cases where quenching or inversion of the Hall resistance occurs, or where there is a large bend resistance at zero magnetic field, collimation of the injected electrons is important. Collimation means that the momentum distribution of injected electrons is weighted towards large parallel momentum due to a gradual widening of the wires near the junction. (2) The resistances obtained from the classical and quantum calculations differ substantially. First, the quantum result at zero temperature is strikingly different from the classical result because of large fluctuations caused by interference between long paths. Such effects are suppressed by temperatures of order 1 K and have been treated elsewhere. In this work we focus on the average quantum behavior, which we extract by two different averaging procedures. The classical and quantum results are in good qualitative agreement; however, we find substantial quantitative differences that persist well into the many-channel (classical) limit. (3) We analyze the classical results in terms of the type of electron trajectory that contributes to the Hall or bend resistance and find that the ballistic anomalies are caused by short trajectories. In particular, we find that long "scrambling" trajectories are not important in producing these anomalies. These conclusions are reinforced and illustrated by quantum calculations of local transport quantities: the charge density, the current density, and the Wigner and Husimi distributions. The collimation of the injected electrons and the importance of specific short trajectories are particularly clear in the Wigner and Husimi distributions.