Universal conductance reduction in a quantum wire

TL;DR

This paper proves that a single point defect in a quantum wire causes a universal conductance reduction of 2e^2/h across all sub-bands, independent of defect specifics, revealing fundamental conductance limits.

Contribution

It provides a rigorous proof of universal conductance reduction and demonstrates defect-independent transmission properties in quantum wires.

Findings

Conductance reduction of exactly 2e^2/h per sub-band due to a point defect

Surface defects lead to universal, defect-independent transmission matrix values

Particle confinement effects between weak point defects analyzed

Abstract

Even a single point defect in a quantum wire causes a conductance reduction. In this paper we prove (without any approximations) that for any point impurity this conductance reduction in all the sub-bands is exactly 2e^2/h. Moreover, it is shown that in the case of a surface defect, not only is the conductance minimum independent of the defect characteristics, but the transmission matrix also converges to universal (defect-independent) values. We also discuss particle confinement between two arbitrarily weak point defects.