Phonons In Quantum Wires Research Articles

Erratum: Electron interaction with confined acoustic phonons in quantum wires subjected to a magnetic field [Phys. Rev. B57, 4687 (1998)

Erratum: Electron interaction with confined acoustic phonons in quantum wires subjected to a magnetic field [Phys. Rev. B<b>57</b>, 4687 (1998)

Electron interaction with confined acoustic phonons in quantum wires subjected to a magnetic field

Electron interaction with confined acoustic phonons in quantum wires subjected to a magnetic field

Electron Relaxation by LO Phonons in Quantum Wires

The adiabatic approximation is used to describe the electron states of weakly-one-dimensional quantum wires. A clear order is evidenced in the longitudinal optical (LO) phonon mediated transition rates with respect to the quantum numbers of the confined states involved. The average single electron relaxation time from an excited level is shown either to increase or, surprisingly; to decrease as a function of the initial energy. The relaxation of an excited population is dynamically simulated, showing the wire size dependent accelerating and energy lowering effects of an additional phenomenological intrasubband thermalization.

Electron relaxation by LO phonons in quantum wires: An adiabatic approach

The electron states of weakly-one-dimensional quantum wires are computed using the adiabatic approximation in the framework of the k . p theory and the envelope-function approximation. The computed transition rates of electrons from one confined state to any other, mediated by the longitudinal optical (LO) phonons, are clearly ordered with respect to the quantum numbers of the states provided by the adiabatic approximation. The average single electron relaxation time from an excited level is shown to either increase or surprisingly decrease as a function of initial energy. Finally, the relaxation dynamics of an excited population of electrons is analyzed. We show that a fast phenomenological intrasubband thermalization, simultaneous to the LO phonon-mediated relaxation, lowers the final average energy and may in some cases significantly speed up the whole relaxation.

Guided Acoustic Phonons in Quantum Wires: Theory of Phonon Fiber

Acoustic phonon modes confined to a GaAs cylindrical quantum wire within AlAs are analytically investigated within the context of an elastic continuum model. Elastic properties are assumed to be isotropic for both materials for mathematical convenience. The displacement vector is expressed by the scalar potential and two vector potentials. The confined acoustic phonon modes are classified into three types according to the rotational symmetry of the potential functions: dilatational, torsional, and flexural modes. Dispersion curves of the modes show phonon subband structures with finite cutoff frequencies due to confinement of waves in lateral directions. The density of the confined phonon modes accordingly appears as staircaselike structures.

Polar-optical oscillations and electron-phonon interaction in quantum wires and quantum dots

A theory for long-wavelength optical phonons in quantum wires and quantum dots is developed under very general conditions. Confined and interface modes are obtained as solutions of the full system of four coupled second-order differential equations for the vibrational amplitudes and the electrostatic potential. These equations are solved without incompatibility between the mechanical and electrostatic matching boundary conditions. The eigensolutions and eigenmodes for cylindrical quantum wires and spherical quantum dots are found in terms of the longitudinal and transverse parts of the mechanical vibrational field and the electrostatic field, all appropriately coupled. The pure surface phonons (Fröhlich phonons) are obtained as a particular case. The orthogonality and the general conditions under which the set of eigensolutions form a complete basis are established. The electron-phonon interaction Hamiltonians are given in explicit form.

Negative absolute conductivity in quantum wires

The effect of negative absolute conductivity in quasi-one-dimensional quantum wire structures is obtained by the Monte Carlo simulation. This negative conductivity is associated with inelastic optical phonon scattering leading to an asymmetric electron distribution function established under conditions of intensive electron photoinjection. Simulation results suggest that quantum wires are ideal for the experimental observation of negative absolute conductivity. The oscillations of photoconductivity as a function of injection energy can reveal the spectrum of optical phonons in quantum wires which differs considerably from that in bulk materials.

Electron high-field transport in multisubband quantum wire structures

The Monte Carlo simulation of electron transport in multisubband quasi-one-dimensional GaAs/AlAs quantum wires (QWIs) are presented. The electron intrasubband and intersubband scattering by surface-optical and confined longitudinal-optical phonons in QWIs has been included in the program. It is demonstrated that at room temperature the electron drift velocity in the QWI is suppressed by electron intersubband scattering and does not exceed the bulk material values. The energy dependence of the total scattering rate in ideal QWIs exhibits multiple sharp peaks related to intersubband transitions. The scattering rates in the real QWIs with variable thicknesses are calculated as well. The results show that even small variation in thickness leads to a significant broadening of the very first peaks and complete washing-out of the peak-like structure at higher energies.

Optical phonons in GaAs/AlAs quantum wires.

Phonon-dispersion curves of semiconductor quantum wires are studied in a realistic rigid-ion model. We introduce an approach for solving the rigid-ion model in quantum wires, which avoids direct computation of the Coulomb interaction. Our calculations demonstrate the interesting anisotropic behavior of long-wavelength optical phonons in quantum wires. In particular, we show that frequencies of several optical phonons approach different values as the wave vector approaches the zone center from three different axes. We have also shown that the lateral confinement in a quantum wire on the interface modes leads to the edge modes.