Quantum ballistic transport in constrictions of n-PbTe

Conductance of submicron constrictions of PbTe:Bi was studied up to 8 T and between 4.2 K and 50 mK(. The structures were fabricated by electron beam lithography and chemical etching of high-electron mobility films grown by molecular beam epitaxy on BaF2. In the moderately strong magnetic fields perpendicular to the current, B greater than or equal to 1 T, the conductance shows accurate quantization in the units of le(2)/h as a function of the side-gate voltage. In the absence of the field, a temperature-independent step structure, with an average step height of approximate to e(2)/h, is observed. It is suggested that such a quantization may reflect the lifting of the Kramers degeneracy by the exchange interaction among the electrons, effective despite a large dielectric constant of bulk PbTe. [S0163- 1829(99)50532-8].