Magnetic field, temperature and spin-polarization effects on electron transport through DNA molecules

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Authors
Alsaid, Alaa Hosain
Advisor
Joe, Yong S.
Issue Date
2020-07-18
Keyword
Degree
Thesis (M.S.)
Department
Department of Physics and Astronomy
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Abstract

The deoxyribonucleic acid (DNA) has been widely recognized as the hereditary material found in all organisms. It consists of four nucleotide bases adenine (A), guanine (G), cytosine (C), and thymine (T) linked to a sugar-phosphate backbone. The hydrogen bonds, together with the base-pairs rules of the nucleotide bases, form the double-stranded DNA strand. This thesis aims to study the theoretical analysis of the electron transmission through a two-dimensional, four-channel DNA model, specifically the effect of the magnetic field, temperature, and electron spin. It also includes the graphical outputs on the transmission, 2-D and 3-D contour plots, Lyapunov coefficient, localization length, current-voltage characteristics, spin polarization, and spinpolarized current. Due to the presence of magnetic flux on DNA, the Aharonov-Bohm oscillation with the periodicity of AB oscillations in the transmission and a semiconductor behavior in I-V characteristics could be observed. The increase in temperature can reduce the electron transmission and conductance of the DNA regardless of its sequencing (i.e. periodic, mismatched, or palindromic). However, the highest current could be found in a periodic DNA sequence. The research findings also show that the double-stranded DNA serves as a perfect spin filter despite the weak spin-obit coupling, and therefore its spin filtration efficiency could be enhanced by increasing the DNA length. Depending on the distance between the replacements of the mispairs and the contacts, and to the number of mispairs, the mismatched sequences could affect the spin polarization. The double-stranded DNA could also act as either a semiconductor or a metal depending on the spin-orbit coupling strength, which shows high spin-polarized current. However, the variation on the helix angle only enables double-stranded DNA to serve as a semiconductor with a high percentage of spin-polarized current at a specific bias voltage.

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