Abstract
The study of spin transport has emerged at the forefront of condensed matter physics during the last decade. Much of the interest has undoubtedly been sparked by the advent of the spintronics paradigm and the idea of creating novel electronic devices based on the spin degree of freedom of the carriers. However, a great deal of interest is due to the rich physics that emerges from the study of spin phenomena. In this thesis we will study quantum spindependent phenomena as it appears in nanoscale structures formed in semiconducting materials. We will set up a formalism for quantum spin transport and apply it to investigate novel coherent spin phenomena such as the spin Hall effect and Zitterbewegung, as well as spin conductance and polarisation in mesoscopic structures. Symmetry relations are derived which sets rigorous constraints on the spin transport properties. We will furthermore consider manybody effects in spinorbit coupled systems and coherent geometrical phase properties due to interaction with a timeperiodic field.
Computational techniques based on the scattering matrix formalism have been developed for spindependent transport in quantum structures with spinorbit interaction and local magnetic field modulations. The techniques have been applied to the studies of the spin Hall effect and Zitterbewegung in both electron and the less studied hole systems, multiterminal spindependent transport with spinorbit interaction, and the problem of creating a source of spinpolarised carriers. In the presence of spinorbit interactions the spin Hall effect arises as a spin accumulation along the transverse edges of a waveguide, and as a spinstripe pattern in the internal part of the waveguide. We show that the Zitterbewegung is directly linked to the spin Hall effect and only differ in the injection conditions. We further find that flux polarisation in a multiterminal structure is strongly influenced by the existence of multiple lead channels and give rise to spinrectification and spinpartitioning. A source of spinpolarised carriers is proposed by demonstrating that a current of large spin polarisation, at a temperature above the spinsplitting temperature, can be achieved in a doubledot structure influenced by a nonuniform magnetic field.
Symmetry considerations are powerful tools to derive rigorous constraints on spin transport properties. By a symmetry analysis we show that the inplane polarisation of hole transport necessarily vanishes whenever the outgoing lead only supports heavy hole channels. It is also shown that the complete spinpolarisation vanishes identically under timereversal symmetry whenever the
outgoing lead supports one, doubly degenerate, hole channel independent of the number of incoming channels or the details of the scatterer.
On the topic of interactions, recent measurements of Coulomb blockade of holes in nanowire quantum dots are analysed by formulating a pseudospin HartreeFock language to extract a hole exchange interaction energy. We furthermore study the geometrical response of quantum confined particles to a timeperiodic electric field and show that fieldinduced angular momentum and spin transitions are associated with a geometrical phase indicating a nontrivial topology of the projective Hilbert space.
Computational techniques based on the scattering matrix formalism have been developed for spindependent transport in quantum structures with spinorbit interaction and local magnetic field modulations. The techniques have been applied to the studies of the spin Hall effect and Zitterbewegung in both electron and the less studied hole systems, multiterminal spindependent transport with spinorbit interaction, and the problem of creating a source of spinpolarised carriers. In the presence of spinorbit interactions the spin Hall effect arises as a spin accumulation along the transverse edges of a waveguide, and as a spinstripe pattern in the internal part of the waveguide. We show that the Zitterbewegung is directly linked to the spin Hall effect and only differ in the injection conditions. We further find that flux polarisation in a multiterminal structure is strongly influenced by the existence of multiple lead channels and give rise to spinrectification and spinpartitioning. A source of spinpolarised carriers is proposed by demonstrating that a current of large spin polarisation, at a temperature above the spinsplitting temperature, can be achieved in a doubledot structure influenced by a nonuniform magnetic field.
Symmetry considerations are powerful tools to derive rigorous constraints on spin transport properties. By a symmetry analysis we show that the inplane polarisation of hole transport necessarily vanishes whenever the outgoing lead only supports heavy hole channels. It is also shown that the complete spinpolarisation vanishes identically under timereversal symmetry whenever the
outgoing lead supports one, doubly degenerate, hole channel independent of the number of incoming channels or the details of the scatterer.
On the topic of interactions, recent measurements of Coulomb blockade of holes in nanowire quantum dots are analysed by formulating a pseudospin HartreeFock language to extract a hole exchange interaction energy. We furthermore study the geometrical response of quantum confined particles to a timeperiodic electric field and show that fieldinduced angular momentum and spin transitions are associated with a geometrical phase indicating a nontrivial topology of the projective Hilbert space.
Original language  English 

Qualification  Doctor 
Awarding Institution 

Supervisors/Advisors 

Award date  2008 Jun 5 
ISBN (Print)  9789162875275 
Publication status  Published  2008 
Bibliographical note
Defence detailsDate: 20080605
Time: 10:15
Place: Room B, Fysicum, Sölvegatan 14, Lund university, Faculty of Engineering
External reviewer(s)
Name: Loss, Daniel
Title: Professor
Affiliation: University of Basel, Switzerland

Subject classification (UKÄ)
 Condensed Matter Physics
Free keywords
 Zitterbewegung.
 spin Hall effect
 spintronics
 Spin
 quantum transport