Giant microwave-induced BB-periodic magnetoresistance oscillations in a two-dimensional electron gas with a bridged-gate tunnel point contact

We have studied the magnetoresistance of the quantum point contact fabricated on the high mobility two-dimensional electron gas (2DEG) exposed to microwave irradiation. The resistance reveals giant $B$-periodic oscillations with the relative amplitude $\Delta R/R$ of up to $700$\% resulting from the propagation and interference of the edge magnetoplasmons (EMPs) in the sample. This giant photoconductance is attributed to the considerably large local electron density modulation in the vicinity of the point contact. We have also analyzed the oscillation periods $\Delta B$ of the resistance oscillations and, comparing the data with the EMP theory, extracted the EMP interference length $L$. We have found that the length $L$ substantially exceeds the distance between the contact leads but rather corresponds to the distance between metallic contact pads measured along the edge of the 2DEG. This resolves existing controversy in the literature and should help to properly design highly sensitive microwave and terahertz spectrometers based on the discussed effect.Comment: 5 pages, 5 figure

Unconventional Hall effect near charge neutrality point in a two-dimensional electron-hole system

The transport properties of the two-dimensional system in HgTe-based quantum wells containing simultaneously electrons and holes of low densities are examined. The Hall resistance, as a function of perpendicular magnetic field, reveals an unconventional behavior, different from the classical N-shaped dependence typical for bipolar systems with electron-hole asymmetry. The quantum features of magnetotransport are explained by means of numerical calculation of the Landau level spectrum based on the Kane Hamiltonian. The origin of the quantum Hall plateau {\sigma}xy = 0 near the charge neutrality point is attributed to special features of Landau quantization in our system.Comment: 8 pages, 7 figure