Charge and Spin Transport in Nanowires with Spin-Orbit Coupling

Nanowires exhibiting Fermi-level pinning have strong radial electron confinement and thus can be modeled as a two-dimensional electron gas wrapped around the core. In III-V semiconductor structures, two forms of spin-orbit coupling are generated by breaking inversion symmetries in the crystal (Dresselhaus) and the overall structure of the nanowires (Rashba). The first goal of this thesis is to understand the single-particle energy spectrum in nanowires with variable cross sections and the quantum oscillations that can be driven in them by the application of a magnetic field parallel to the axis of the wire. To this end, the eigenfunctions and eigenvalues of the Hamiltonian are evaluated numerically in a finite difference method that allows the implementation of all the interactions acting in the system for the particular symmetry of a given wire. Then, using the single-particle energies and eigenfunctions, we investigate the NW transport properties under the action of electric fields or thermal gradients. In the linear regime, we discuss both a ballistic model and a diffusive approximation based on the Boltzmann transport equation to evaluate charge conductivity and the Seebeck coefficients in a nanowire with a circular cross-section. In the non-linear regime, quadratic in the electric field, spin-currents azimuthally polarized are created on account of the spin-orbit interaction. The dependence of these currents on the coupling constants of the spin-orbit interactions is studied.