Spin alignment of electrons in PbTe/(Pb,Eu)Te nanostructures

We have measured the transport properties of one-dimensional electron gas fabricated of narrow gap semiconductor, PbTe. The Zeeman splitting in this material is comparable to the cyclotron energy and may be as large as View the MathML source. Submicron constrictions have been patterned by electron beam lithography of View the MathML source PbTe quantum well embedded between Bi-doped Pb0.92Eu0.08Te barriers grown by MBE onto View the MathML source Pb0.92Eu0.08Te-undoped buffer layer and BaF2 substrate. The constriction conductance is tuned by the gate voltage applied across an interfacial p–n junction. At helium temperatures, we observe a sequence of conductance plateaux with values equal to i×2e2/h. For certain integers i, the plateaux are absent indicating one-dimensional mode degeneracy. This points to an oval shape of the conductor cross section with two equivalent transverse quantization directions. In a perpendicular magnetic field, we start to observe the spin resolved half-integer plateaux already at View the MathML source. Moreover, above View the MathML source, we find a complex evolution of the plateau sequence resulting from the fact that the Zeeman splitting becomes larger than the separation between the one-dimensional energy levels. This leads to an unusual situation when entirely spin-polarized electron current is carried by several electric subbands.