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Description:
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This dissertation focuses on the study of spin -dependent transport in systems
with strong spin -orbit coupling within their band structure . In particular we focus
on the anomalous Hall effect , the spin Hall effect , and the Aharonov -Casher effect
whose origins , are linked to the presence of spin -orbit coupling . Given the theoretical
controversy surrounding these effects we further simplify our studies to semiconductor
systems where the band structure is much simpler than in metallic systems with heavy
elements . To obtain finite analytical results we focus on reduced dimensions (two and
one dimensions ) which can be explored experimentally . To set the stage , we discuss
the origins of the strong spin -orbit coupling in semiconductors deriving the effective
interaction from the Dirac equation . We discuss in detail the skew scattering contribution
to the anomalous Hall effect in two -dimensional systems , which is dominant
for systems with low impurity concentrations , and find that it is reduced when the
two chiral subbands are partially occupied in an electron gas and vanishes for a hole
gas , regardless of the band filling . We also present calculations for all contributing
mechanisms . We propose a device to test this prediction and study the crossover from
the intrinsic to the extrinsic anomalous Hall effect . We calculate all contributions to
the anomalous Hall effect in electron systems using the Kubo -Streda formalism . We
find that all contributions vanish when both subbands are occupied and that the
skew scattering contribution dominates when only the majority subband is occupied .
We calculate the interference effects due to spin -orbit interaction in mesoscopic ring structures patterned from HgTe quantum wells related to the Aharonov -Casher effect
and the spin Hall effect . We find that the transport properties are affected by the
carrier density as well as the spin orbit interaction . We find that the conductivity is
larger in hole gas systems . We also show that devices with inhomogenous spin orbit
interaction exhibit an electrically controlled spin -flipping mechanism . |