SHOT NOISE SUPPRESSION IN QUANTUM POINT CONTACT STRUCTURES

The shot noise power spectrum of a quantum point contact structure is investigated based upon a time-dependent Landauer approach. The system is modeled by an open conducting channel coupled with two infinite reservoirs. When the channel length L ≫ ξ (the coherence length of an electron wave packet), all the channel states moving from source to drain are fully occupied while all the opposite ones are empty. Consequently, shot noise is suppressed to zero along with conductance quantization. For L ~ ξ, however, while the conductance is still well quantized, the shot noise is only partially suppressed to a nonzero fraction of its full level, in agreement with recent experimental data.