Electron--Electron Scattering in Quantum Wires and it's Possible Suppression due to Spin Effects

A microscopic picture of electron-electron pair scattering in single mode quantum wires is introduced which includes electron spin. A new source of `excess' noise for hot carriers is presented. We show that zero magnetic field `spin' splitting in quantum wires can lead to a dramatic `spin'-subband dependence of electron--electron scattering, including the possibility of strong suppression. As a consequence extremely long electron coherence lengths and new spin-related phenomena are predicted. Since electron bands in III-V semiconductor quantum wires are in general spin-split in zero applied magnetic field, these new transport effects are of general importance.Comment: 11 pages, LaTeX and APS-RevteX 2, Rep.No. GF66,Figures from author, Physical Review Letters, scheduled for 7 June 199

Manifestation of the magnetic depopulation of one-dimensional subbands in the optical absorption of acoustic magnetoplasmons in side-gated quantum wires

We have investigated experimentally and theoretically the far-infrared (FIR) absorption of gated, deep-mesa-etched GaAs/Al$_x$Ga$_{1-x}$As quantum wires. To overcome Kohn's theorem we have in particular prepared double-layered wires and studied the acoustic magnetoplasmon branch. We find oscillations in the magnetic-field dispersion of the acoustic plasmon which are traced back to the self-consistently screened density profile in its dependence on the magnetic depopulation of the one-dimensional subbands.Comment: LaTeX-file, 4 pages with 3 included ps-figures, to appear in Physica

Plasmons in coupled bilayer structures

We calculate the collective charge density excitation dispersion and spectral weight in bilayer semiconductor structures {\it including effects of interlayer tunneling}. The out-of-phase plasmon mode (the ``acoustic'' plasmon) develops a long wavelength gap in the presence of tunneling with the gap being proportional to the square root (linear power) of the tunneling amplitude in the weak (strong) tunneling limit. The in-phase plasmon mode is qualitatively unaffected by tunneling. The predicted plasmon gap should be a useful tool for studying many-body effects.Comment: 10 pages, 6 figures. to appear in Phys. Rev. Let

Many-body correlations probed by plasmon-enhanced drag measurements in double quantum well structures

Electron drag measurements of electron-electron scattering rates performed close to the Fermi temperature are reported. While evidence of an enhancement due to plasmons, as was recently predicted [K. Flensberg and B. Y.-K. Hu, Phys. Rev. Lett. 73, 3572 (1994)], is found, important differences with the random-phase approximation based calculations are observed. Although static correlation effects likely account for part of this difference, it is argued that correlation-induced multiparticle excitations must be included to account for the magnitude of the rates and observed density dependences.Comment: 4 pages, 3 figures, revtex Accepted in Phys. Rev.

Correlation induced phonon softening in low density coupled bilayer systems

We predict a possible phonon softening instability in strongly correlated coupled semiconductor bilayer systems. By studying the plasmon-phonon coupling in coupled bilayer structures, we find that the renormalized acoustic phonon frequency may be softened at a finite wave vector due to many-body local field corrections, particularly in low density systems where correlation effects are strong. We discuss experimental possibilities to search for this predicted phonon softening phenomenon.Comment: 4 pages with 2 figure

Carrier relaxation due to electron-electron interaction in coupled double quantum well structures

We calculate the electron-electron interaction induced energy-dependent inelastic carrier relaxation rate in doped semiconductor coupled double quantum well nanostructures within the two subband approximation at zero temperature. In particular, we calculate, using many-body theory, the imaginary part of the full self-energy matrix by expanding in the dynamically RPA screened Coulomb interaction, obtaining the intrasubband and intersubband electron relaxation rates in the ground and excited subbands as a function of electron energy. We separate out the single particle and the collective excitation contributions, and comment on the effects of structural asymmetry in the quantum well on the relaxation rate. Effects of dynamical screening and Fermi statistics are automatically included in our many body formalism rather than being incorporated in an ad-hoc manner as one must do in the Boltzman theory.Comment: 26 pages, 5 figure

Uncoupled excitons in semiconductor microcavities detected in resonant Raman scattering

We present an outgoing resonant Raman-scattering study of a GaAs/AlGaAs based microcavity embedded in a p-i-n junction. The p-i-n junction allows the vertical electric field to be varied, permitting control of exciton-photon detuning and quenching of photoluminescence which otherwise obscures the inelastic light scattering signals. Peaks corresponding to the upper and lower polariton branches are observed in the resonant Raman cross sections, along with a third peak at the energy of uncoupled excitons. This third peak, attributed to disorder activated Raman scattering, provides clear evidence for the existence of uncoupled exciton reservoir states in microcavities in the strong-coupling regime

Coulomb Blockade Resonances in Quantum Wires

The conductance through a quantum wire of cylindrical cross section and a weak bulge is solved exactly for two electrons within the Landauer-Buettiker formalism. We show that this 'open' quantum dot exhibits spin-dependent Coulomb blockade resonances resulting in two anomalous structure on the rising edge to the first conductance plateau, one near 0.25(2e^2/h), related to a singlet resonance, and one near 0.7(2e^2/h), related to a triplet resonance. These resonances are generic and robust, occurring for other types of quantum wire and surviving to temperatures of a few degrees.Comment: 5 pages, 3 postscript files with figures; uses REVTe

Effect of the spin-orbit interaction on the band structure and conductance of quasi-one-dimensional systems

We discuss the effect of the spin-orbit interaction on the band structure, wave functions and low temperature conductance of long quasi-one-dimensional electron systems patterned in two-dimensional electron gases (2DEG). Our model for these systems consists of a linear (Rashba) potential confinement in the direction perpendicular to the 2DEG and a parabolic confinement transverse to the 2DEG. We find that these two terms can significantly affect the band structure introducing a wave vector dependence to subband energies, producing additional subband minima and inducing anticrossings between subbands. We discuss the origin of these effects in the symmetries of the subband wave functions.Comment: 15 pages including 14 figures; RevTeX; to appear in Phys.Rev.B (15 Nov 1999