超微结构中的Landauer-Buttiker输运理论

LANDAUER-BUTTIKER TRANSPORT THEORY IN MESOSCOPIC STRUCTURES

随着超微结构或者所谓的介观结构的尺度不断缩小而逼近各种描述固体属性的特征长度(相位相干长度、弹性散射长度或者布洛赫波长)时电子波函数的量子属性在介观结构的输运现象中表现得越来越明显。近年来发展日趋完善的Landauer-Buttiker输运理论由于明确考虑了波函数相位对输运的影响,在介释介观结构中各种量子相干输运现象时获得了很大的成功。本文力图较系统地介绍Landauer-Buttiker输运理论的要点,讨论介观结构中电导的对称性、电势分布的涨落和电势电极引起的相干性等重要问题。有关计算介观结构各电极间的散射矩阵S或者透射系数的微观理论不属本文讨论范围之内。

With continuously scaling down in the dimensional size of microst-ructures or so-called mesoscopic structures, the quantum nature of electronic wave functions manifests itself more and more obviously in the transport phenomena of the mesoscopic structures as their sizes approach to various characteristic lengths underlying corresponding physical properties such as phase-coherent length, elastic scattering length or Bloch wave length . By explicitly taking into account the effects of the phase of the wave function, the recentwell-developed Landauer-Buttiker transport theory has very succeeded in explaining various quantum-coherent transports observed in the mesoscopic structures. The present paper aims to systematically review the essenial features of the Landauer-Biittiker formalism and discuss several important issues such as the symmetry of the conductance, the fluctuation of potential distribution and the coherence incurred by potential probes etc.,. The microscopic theory for calculating the scattering matrix or the transmission probability between the probes of the structure will be out of the scope of this paper.