CIRCUIT-THEORY IN BALLISTIC CONDUCTING CHANNEL

A new approach to derive the Landauer formula is developed by treating the current flowing ballistic conducting channel as an open system, i n which an electronic distribution function shifts in proportion to an external current flow. The effect of an open system is taken into acc ount by means of the Lagrange multiplier. By introducing current refle ction and transmission coefficients, and by explicitly treating the vo ltage drop under the condition that the contact between the lead and t he electrode is ideal, two types of circuit equations corresponding to two Landauer formulas are obtained. In our analysis, the Landauer for mula is not reproduced when there are no scattering centers in each le ad, i.e., each lead is ideal, but is reproduced when there is no elast ic scattering and the phase coherence is lost in each lead.