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We observe an adiabatic transport phenomena of electrons in valley-splitting quantum Hall edge channels for the first time using a high-mobility Si/SiGe two-dimensional electron system. We find that the scattering event between the valley-splitting edge channels is suppressed over a distance of ā5 Ī¼m, which is surprisingly longer than that expected from the valley-splitting energy gap in Si. |
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We study the edge-channel transport at quantum Hall (QH) transition regions for a high-mobility Si / Si Ge QH conductor by measuring nonlocal resistance (RNL). TheĀ RNLĀ as a function of magnetic field changes drastically after Landau-level crossings. The features of theĀ RNLĀ depend on the spin configuration between the innermost edge channel and the bulk state: theĀ RNLĀ appears only when the relevant edge-bulk states have opposite spin orientations. Also, an origin of the spin-dependent resistivity [Phys. Rev. Lett. 94, 176402 (2005)] at QH transition regions is discussed in terms of the spin-dependent inter-edge-bulk scattering. |
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The authors have developed a method for electrical polarization of nuclear spins in quantum Hall systems. In a breakdown regime of odd-integer quantum Hall effect (QHE), excitation of electrons to the upper Landau subband with opposite spin polarity dynamically polarizes nuclear spins through the hyperfine interaction. The polarized nuclear spins in turn accelerate the QHE breakdown, leading to hysteretic voltage-current characteristics of the quantum Hall conductor. |