Fractional quantization of the ballistic conductance in one dimensional hole systems

We analyze the fractional quantization of the ballistic conductance associated with the light and heavy hole bands in Si, Ge, and GaAs systems. It is shown that the formation of a localized hole state in the region of the quantum point contact connecting two quasi-one-dimensional hole leads drastically modifies the conductance pattern. The exchange interaction between localized and propagating holes results in fractional quantization of the ballistic conductance unlike that in electronic systems. The value of the conductance at the additional plateaus depends on the offset between the bands of the light and heavy holes, Δ, and the sign of the exchange interaction constant. For Δ=0 and ferromagnetic exchange interaction, we observe additional plateaus around the values 7 e2/4h, 3 e2/h, and 15 e2/4h, while antiferromagnetic interaction plateaus are formed around e2/4h, e2/h, and 9 e2/4h. For large Δ, a single plateau is formed at e2/h.