Observation of chiral heat transport in the quantum Hall regime

Heat transport in the quantum Hall regime is investigated using micron-scale heaters and thermometers positioned along the edge of a millimeter-scale two dimensional electron system (2DES). The heaters rely on localized current injection into the 2DES, while the thermometers are based on the thermoelectric effect. In the v=1 integer quantized Hall state, a thermoelectric signal appears at an edge thermometer only when it is “downstream,” in the sense of electronic edge transport, from the heater. When the distance between the heater and the thermometer is increased, the thermoelectric signal is reduced, showing that the electrons cool as they propagate along the edge

Hot-electron thermocouple and the diffusion thermopower of two-dimensional electrons in GaAs

A simple hot-electron thermocouple is realized in a two-dimensional electron system (2DES) and used to measure the diffusion thermopower of the 2DES at zero magnetic field. This hot-electron technique, which requires no micron-scale patterning of the 2DES, is much less sensitive than conventional methods to phonon-drag effects. Our thermopower results are in good agreement with the Mott formula for diffusion thermopower for temperatures up to T~2 K

Tunneling and nonlinear transport in a vertically coupled GaAs/AlGaAs double quantum wire system

We report low-dimensional tunneling in an independently contacted vertically coupled quantum wire system. This nanostructure is fabricated in a high quality GaAs/AlGaAs parallel double quantum well heterostructure. Using a novel flip chip technique to align top and bottom split gates to form low-dimensional constrictions in each of the independently contacted quantum wells we explicitly control the subband occupation of the individual wires. In addition to the expected 2D-2D tunneling results, we have found additional tunneling features that are related to the 1D quantum wires.Comment: 4 pages, 3 figures, submitted to APL Minor revision

Undoped Electron-Hole Bilayers in a GaAs/AlGaAs Double Quantum Well

We present the fabrication details of completely undoped electron-hole bilayer devices in a GaAs/AlGaAs double quantum well heterostructure with a 30 nm barrier. These devices have independently tunable densities of the two-dimensional electron gas and two-dimensional hole gas. We report four-terminal transport measurements of the independently contacted electron and hole layers with balanced densities from $1.2 \times 10^{11}$cm$^{-2}$ down to $4 \times 10^{10}$ cm$^{-2}$ at $T = 300 mK$. The mobilities can exceed $1 \times 10^{6}$ cm$^{2}$ V$^{-1}$ s$^{-1}$ for electrons and $4 \times 10^{5}$ cm$^{2}$ V$^{-1}$ s$^{-1}$ for holes.Comment: 3 pages, 3 figure

Oscillatory Magneto-Thermopower and Resonant Phonon Drag in a High-Mobility 2D Electron Gas

Experimental and theoretical evidence is presented for new low-magnetic-field ($B<5$ kG) 1/B-oscillations in the thermoelectric power of a high-mobility GaAs/AlGaAs two-dimensional (2D) electron gas. The oscillations result from inter-Landau-Level resonances of acoustic phonons carrying a momentum equal to twice the Fermi wavenumber at $B = 0$. Numerical calculations show that both 3D and 2D phonons can contribute to this effect.Comment: 4 pages, 5 figure