Plasmon-pole approximation for semiconductor quantum wire electrons

We develop the plasmon-pole approximation for an interacting electron gas confined in a semiconductor quantum wire. We argue that the plasmon-pole approximation becomes a more accurate approach in quantum wire systems than in higher dimensional systems because of severe phase-space restrictions on particle-hole excitations in one dimension. As examples, we use the plasmon-pole approximation to calculate the electron self-energy due to the Coulomb interaction and the hot-electron energy relaxation rate due to LO-phonon emission in GaAs quantum wires. We find that the plasmon-pole approximation works extremely well as compared with more complete many-body calculations.Comment: 16 pages, RevTex, figures included. Also available at http://www-cmg.physics.umd.edu/~lzheng

Inelastic lifetimes of confined two-component electron systems in semiconductor quantum wire and quantum well structures

We calculate Coulomb scattering lifetimes of electrons in two-subband quantum wires and in double-layer quantum wells by obtaining the quasiparticle self-energy within the framework of the random-phase approximation for the dynamical dielectric function. We show that, in contrast to a single-subband quantum wire, the scattering rate in a two-subband quantum wire contains contributions from both particle-hole excitations and plasmon excitations. For double-layer quantum well structures, we examine individual contributions to the scattering rate from quasiparticle as well as acoustic and optical plasmon excitations at different electron densities and layer separations. We find that the acoustic plasmon contribution in the two-component electron system does not introduce any qualitatively new correction to the low energy inelastic lifetime, and, in particular, does not produce the linear energy dependence of carrier scattering rate as observed in the normal state of high-$T_c$ superconductors.Comment: 16 pages, RevTeX, 7 figures. Also available at http://www-cmg.physics.umd.edu/~lzheng

Thermoelectric composites of poly(3-hexylthiophene) and carbon nanotubes with a large power factor

Composite films of poly(3-hexylthiophene) and single- as well as multi-walled carbon nanotubes are demonstrated to offer a competitive thermoelectric performance. The power factor significantly exceeds values obtained with either constituent alone provided that the conjugated polymer is sufficiently p-doped. The use of single-walled carbon nanotubes consistently results in a higher electrical conductivity with a maximum value above 10(3) S cm(-1) and thus gives rise to a power factor of 25 +/- 6 mu W m(-1) K-2 for a filler content of only 8 wt% and a maximum 95 +/- 12 mu W m(-1) K-2 for 42-81 wt%. Moreover, a carbon nanotube content of 8-10 wt% does not compromise the low bulk thermal conductivity of the polymer matrix, which promises a high figure of merit of at least ZT > 10(-2) at room-temperature. All samples are cast on plastic substrates, emphasising their suitability for large-area, flexible thermoelectric applications

Effect of finite-temperature local field corrections on many-body properties of quantum wires

73.21.Hb Quantum wires, 71.10.Ca Electron gas, Fermi gas, 71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons,