University of Twente Student Theses


Numerical calculation of magnetoresistance in a thin-film Bi2Te3 topological insulator

Ruiter, D.R. de (2016) Numerical calculation of magnetoresistance in a thin-film Bi2Te3 topological insulator.

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Abstract:The magnetoresistance is calculated for thin-film Bi2Te3, a topological insulator. As a first step, the band structure is obtained through self-consistently solving a set of coupled Schrödinger-Poisson equations within the numerical package NEMO5. The Schrödinger equation is solved using a tight-binding Hamiltonian. The Poisson equation is solved by a FEM routine. As a next step, the group velocities, effective masses and wave function overlaps are obtained from the band structure. With these results, the conductivity is calculated by solving the linearized Boltzmann equation. A nonzero electrostatic potential is fixed on one of the surfaces, to mimic gating and the presence of charged adsorbates on the surface. Effects of a magnetic field on the band structure and on the alignment of the spin are investigated. The resulting energy shifts of the bands are smaller than observed in literature. The calculations for the magnetoresistance do not predict positive, linear magnetoresistance when only topological surface states contribute to the transport. When bulk conduction bands contribute as well, positive magnetoresistance is observed.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:31 mathematics
Programme:Applied Mathematics MSc (60348)
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