Unconventional reentrant quantum Hall effect in a HgTe/CdHgTe double quantum well

International audienceWe report on observation of an unconventional structure of the quantum Hall effect (QHE) in a p-type HgTe/CdxHg1−xTe double quantum well (DQW) consisting of two HgTe layers of critical width. The observed QHE is a reentrant function of magnetic field between two i = 2 states (plateaus at ρxy = h/ie 2) separated by an intermediate i = 1 state, which looks like some anomalous peak on the extra-long i = 2 plateau when weakly expressed. The anomalous peak apparently separates two different regimes: a traditional QHE at relatively weak fields for a small density of mobile holes ps and a high-field QH structure with a 2 − 1 plateau-plateau transition corresponding to much larger ps. We show that only a part of holes, residing in an additional light hole subband in the DQW, participate in QHE at weak fields while the rest of holes is excluded into the reservoir formed in the lateral maximum of the valence subband. All the holes come into play at high fields due to a peculiar behavior of the zero-mode levels

Rashba Spin Splitting in HgCdTe Quantum Wells with Inverted and Normal Band Structures

In quantum wells (QWs) formed in HgCdTe/CdHgTe heterosystems with a variable composition of Cd(Hg), Shubnikov-de-Haas (SdH) oscillations are investigated to characterize the Rashba-type spin-orbit coupling in QWs with both a normal and inverted band structure. Several methods of extracting the Rashba spin-splitting at zero magnetic field and their magnetic field dependences from the beatings of SdH oscillations are used for greater reliability. The large and similar Rashba splitting (25–27 meV) is found for different kinds of spectrum, explained by a significant fraction of the p-type wave functions, in both the E1 subband of the sample with a normal spectrum and the H1 subband for the sample with an inverted one