Electronic structure and transport from density matrices and density functionals
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School of Science |
Doctoral thesis (article-based)
| Defence date: 2012-12-14
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Language
en
Pages
64 + app. 33
Series
Aalto University publication series DOCTORAL DISSERTATIONS, 170/2012
Abstract
As a link between theory and experiment, computational physics has received increasingattention in the last decades. Powerful supercomputers provide the possibility of accuratecalculations for large systems, while highly advanced experimental tools allow researchers toconduct experiments on mesoscopic scale. Such developments lead to a bigger overlap areabetween these two fields of physics. On the other hand, computational approaches are based on theories that are under constantenhancement in order to obtain more accurate results, and therefore, both application andtheory development have crucial role in this field of physics. In the present dissertation, we contribute to the both parts. In the first part, we apply the density functional approach on carbon-nanotube-based systems, and we study the effect of defects addatoms, impurities, and their periodicity on the electronic transport properties of the systems. We also predict the formation of Schottky barrier in the junction between two metallic and semiconducting nanotubes. The second part is dedicated to study the challenges and difficulties in time dependent reduced density matrix approaches. We show that the current approximations make the time evolution of two-body reduced density matrix very unstable. We study the possible reasons behind such behavior, and this might lead us to more stable approximations.Description
Supervising professor
Nieminen, Risto, Prof, Aalto University, FinlandOther note
Parts
- [Publication 1]: J. A. Fürst, J. Hashemi, T. Markussen, M. Brandbyge, A. P. Jauho, and R. M. Nieminen. Electronic transport properties of fullerene functionalized carbon nanotubes: Ab initio and tight-binding calculations. Physical Review B, 80, 035427, 2009.
- [Publication 2]: M. J. Hashemi, K. Sääskilahti, and M. J. Puska. Local semiconducting transition in armchair carbon nanotubes: The effect of periodic bi-site perturbation on electronic and transport properties of carbon nanotubes. Physical Review B, 83, 115411, 2011.
- [Publication 3]: P. Havu, M. J. Hashemi, M. Kaukonen, E. T. Seppälä, and R. M. Nieminen. Effect of gating and pressure on the electronic transport properties of crossed nanotube junctions: formation of a Schottky barrier. Journal of Physics: Condensed Matter, 23, 112203, 2011.
- [Publication 4]: A. Akbari, M. J. Hashemi, A. Rubio, R. M. Nieminen, and R. van Leeuwen. Challenges in truncating the hierarchy of time-dependent reduced density matrices equations. Physical Review B, 85, 235121, 2012.