Effects of Electron-Electron Scattering on Electron-Beam Propagation in a Two-Dimensional Electron-Gas

We have studied experimentally and theoretically the influence of electron-electron collisions on the propagation of electron beams in a two-dimensional electron gas for excess injection energies ranging from zero up to the Fermi energy. We find that the detector signal consists of quasiballistic electrons, which either have not undergone any electron-electron collisions or have only been scattered at small angles. Theoretically, the small-angle scattering exhibits distinct features that can be traced back to the reduced dimensionality of the electron system. A number of nonlinear effects, also related to the two-dimensional character of the system, are discussed. In the simplest situation, the heating of the electron gas by the high-energy part of the beam leads to a weakening of the signal of quasiballistic electrons and to the appearance of thermovoltage. This results in a nonmonotonic dependence of the detector signal on the intensity of the injected beam, as observed experimentally.Comment: 9 pages, 7 figure

Ultrafast nonlocal collective dynamics of Kane plasmon-polaritons in a narrow-gap semiconductor

The observation of ultrarelativistic fermions in condensed-matter systems has uncovered a cornucopia of novel phenomenology as well as a potential for effective ultrafast light engineering of new states of matter. While the nonequilibrium properties of two- and three-dimensional (2D and 3D) hexagonal crystals have been studied extensively, our understanding of the photoinduced dynamics in 3D single-valley ultrarelativistic materials is, unexpectedly, lacking. Here, we use ultrafast scanning near-field optical spectroscopy to access and control nonequilibrium large-momentum plasmon-polaritons in thin films of a prototypical narrow-bandgap semiconductor Hg0.81Cd0.19Te. We demonstrate that these collective excitations exhibit distinctly nonclassical scaling with electron density characteristic of the ultrarelativistic Kane regime and experience ultrafast initial relaxation followed by a long-lived highly coherent state. Our observation and ultrafast control of Kane plasmon-polaritons in a semiconducting material using light sources in the standard telecommunications fiber-optics window open a new avenue toward high-bandwidth coherent information processing in next-generation plasmonic circuits

Quantum effects in thermal and thermo-electric transport in semiconductor nanostructures

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Thermal and thermo-electric transport properties of quantum point contacts

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Thermo-electric properties of quantum point contacts

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Magnetoconductance of two point contacts in series

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Selective backscattering and the breakdown of the quantum Hall effect

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Voltage-probe-controlled breakdown of the quantum Hall effect

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Quantum oscillations in the transverse voltage of a channel in the non-linear transport regime

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Sawtooth-like thermopower oscillations of a quantum dot in the Coulomb blockade regime

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe