c of the spin-polarized edge channels in a quantum spin Hall insulator. Experimental setup on a sixterminal Hall bar showing pairs of edge states, with spin-up states in blue and spin-down states in red. Spin-dependent scattering near the Hall contact is provided by the varying the Vxy voltage.

quantum conductance staircase of holes, Gxx, that was measured as a function of the Vxy bias voltage in the ptype silicon quantum well confined by the δ-barriers heavily doped with boron, which is prepared in the framework of the Hall geometry. The fractional conductance features observed at the values of, and are evidence of the prevailing ferromagnetic exchange interaction that gives rise to the spin polarization of holes in a zero magnetic field. This quantum conductance staircase measured to a maximum of, with the plateaus and steps that bring into correlation respectively with the odd and even fractional values, seems to reveal the formation of the helical edge channels in the p-type silicon quantum well.

5. Acknowledgements

The work was supported by the programme of fundamental studies of the Presidium of the Russian Academy of Sciences “Quantum Physics of Condensed Matter” (grant 9.12); programme of the Swiss National Science Foundation (grant IZ73Z0_127945/1); the Federal Targeted Programme on Research and Development in Priority Areas for the Russian Science and Technology Complex in 2007-2012 (contract No. 02.514.11.4074), the SEVENTH FRAMEWORK PROGRAMME Marie Curie Actions PIRSES-GA-2009-246784 project SPINMET.

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