Disorder suppression and precise conductance quantization in constrictions of PbTe quantum wells

Abstract

Conductance quantization was measured in submicron constrictions of PbTe, patterned into narrow $12\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ wide quantum wells deposited between ${\mathrm{Pb}}_{0.92}{\mathrm{Eu}}_{0.08}\mathrm{Te}$ barriers. Because the quantum confinement imposed by the barriers is much stronger than the lateral one, the one-dimensional electron energy-level structure is very similar to that usually met in constrictions of $\mathrm{Al}\mathrm{Ga}\mathrm{As}∕\mathrm{Ga}\mathrm{As}$ heterostructures. However, in contrast to any other system studied thus far, we observe precise conductance quantization in $2{e}^{2}∕h$ units, despite of a significant amount of charged defects in the vicinity of the constriction. We show that such extraordinary results is a consequence of the paraelectric properties of PbTe, namely, the suppression of long-range tails of the Coulomb potentials due to the huge dielectric constant.