Quantum ballistic phenomena in nanostructures of paraelectric PbTe

Abstract

This article reviews recent developments in the physics of lead telluride nanostructures. PbTe is a IV-VI narrow gap paraelectric semiconductor, characterized by the huge static dielectric constant ε>1000 at helium temperatures. Methods of gating and nanostructure fabrication of modulation doped PbTe Pb1-x Eux Te quantum wells are described. Specific properties of PbTe, make it possible to put into evidences a number of interesting effects in the quantum ballistic regime, not encountered in standard semiconductor nanostructures. It is found that conductance of narrow constrictions shows precise zero-field quantization in 2 e2 h units, despite a significant amount of charged defects in the vicinity of the conducting channel. This unusual result is a consequence of a strong suppression of Coulomb potential fluctuations in PbTe, an effect confirmed by numerical simulations. Furthermore, orbital degeneracy of electron waveguide modes can be controlled by the width of PbTe Pb1-x Eux Te quantum wells, so that unusual sequences of plateau conductance are observed. Finally, because of a rather large Zeeman splitting in PbTe, significant spin splitting of the conductance plateaus is observed already in the magnetic fields of about 0.2 T. It is shown that PbTe quantum wires act as efficient local spin-filters, in which the spin polarized current is carried by a large number of wire modes. © 2007 American Institute of Physics.