Theoretical Studies of Electron Transport in Quantum Dot Structures
(2004) Abstract
 We calculate the phase property of the reflection coefficient in twoterminal structures using a lattice tightbinding model. It is seen that, provided that there exist two coherent reflection paths, the reflection probability can be zero for certain electron energies. At these energies, the phase of the reflection coefficient shift abruptly by $pi$.
Next, we study the reflection and transmission phase properties of twoterminal structures coupled to a third lead. The systems are effectivley threeterminal and current conservation is broken with regard to the original twoterminal systems. Two structures, a waveguide with an attached stub quantum dot and a waveguide with an inline, doublebarrier confined quantum dot,... (More)  We calculate the phase property of the reflection coefficient in twoterminal structures using a lattice tightbinding model. It is seen that, provided that there exist two coherent reflection paths, the reflection probability can be zero for certain electron energies. At these energies, the phase of the reflection coefficient shift abruptly by $pi$.
Next, we study the reflection and transmission phase properties of twoterminal structures coupled to a third lead. The systems are effectivley threeterminal and current conservation is broken with regard to the original twoterminal systems. Two structures, a waveguide with an attached stub quantum dot and a waveguide with an inline, doublebarrier confined quantum dot, are considered. The
transmission and reflection phase properties are calculated for these systems with different couplings to the third lead. The results show that the discontinuous phase shifts seen in the currentconserved twoterminal systems are removed when the third lead is attached. However, as long as the coupling between the quantum systems and the additional lead is weak, sharp but continuous phase drops
within narrow energy ranges can still be clearly identified.
Finally, transport through a diatomic asymmetric artificial molecule (double quantum dot) in the nonlinear response regime is studied by means of the same model, but now including selfconsistent electronelectron interactions in the HartreeFock approximation. This approach takes into account the delocalized quantum states of the two coupled quantum dots. The currentvoltage characteristic is found to be strongly nonlinear and strikingly different for opposite bias polarities,
indicating a possibility for the structure to be utilized as a current rectifier. We also find that it is possible to obtain spinpolarized currents. The observed features are found to result from an interplay between Pauli spin blockade and transmission through molecular states, the
localizations of which are sensitive to the applied bias. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/738757
 author
 Fasth, Carina ^{LU}
 supervisor

 Hongqi Xu ^{LU}
 organization
 publishing date
 2004
 type
 Thesis
 publication status
 published
 subject
 language
 English
 LU publication?
 yes
 id
 1518081645344668beb6aec2859cebf8 (old id 738757)
 date added to LUP
 20071211 14:08:12
 date last changed
 20180529 11:29:26
@misc{1518081645344668beb6aec2859cebf8, abstract = {We calculate the phase property of the reflection coefficient in twoterminal structures using a lattice tightbinding model. It is seen that, provided that there exist two coherent reflection paths, the reflection probability can be zero for certain electron energies. At these energies, the phase of the reflection coefficient shift abruptly by $pi$. <br/><br> <br/><br> Next, we study the reflection and transmission phase properties of twoterminal structures coupled to a third lead. The systems are effectivley threeterminal and current conservation is broken with regard to the original twoterminal systems. Two structures, a waveguide with an attached stub quantum dot and a waveguide with an inline, doublebarrier confined quantum dot, are considered. The<br/><br> transmission and reflection phase properties are calculated for these systems with different couplings to the third lead. The results show that the discontinuous phase shifts seen in the currentconserved twoterminal systems are removed when the third lead is attached. However, as long as the coupling between the quantum systems and the additional lead is weak, sharp but continuous phase drops<br/><br> within narrow energy ranges can still be clearly identified.<br/><br> <br/><br> Finally, transport through a diatomic asymmetric artificial molecule (double quantum dot) in the nonlinear response regime is studied by means of the same model, but now including selfconsistent electronelectron interactions in the HartreeFock approximation. This approach takes into account the delocalized quantum states of the two coupled quantum dots. The currentvoltage characteristic is found to be strongly nonlinear and strikingly different for opposite bias polarities,<br/><br> indicating a possibility for the structure to be utilized as a current rectifier. We also find that it is possible to obtain spinpolarized currents. The observed features are found to result from an interplay between Pauli spin blockade and transmission through molecular states, the<br/><br> localizations of which are sensitive to the applied bias.}, author = {Fasth, Carina}, language = {eng}, note = {Licentiate Thesis}, title = {Theoretical Studies of Electron Transport in Quantum Dot Structures}, year = {2004}, }