Quantum point contact with a large localized spin: Fractional quantization of the ballistic conductance

We analyze the conductance of the quantum point contact containing large localized spin J. The additional plateau is formed on a ballistic conductance staircase if only one propagating channel is rendered conducting. The conductance value at this plateau is shown to depend strongly on J and decrease from 3 e2 2h to e2 h when J increases from 1 2 to infinity, which is in a good agreement with the experimental observations.