The Electron Transport in Topological Insulator

• Main Authors: Jiun-Yue Liu, 劉俊岳
• Other Authors: 張慶瑞
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/01402174191937907934

碩士 === 國立臺灣大學 === 物理研究所 === 99 === Under the effect of strong spin-orbit coupling, the new insulator state is found and given the name ``topological insulator,'' which is insulator in the bulk but conductor on the surface. The spin-dependent transport phenomena are analysed by the Landauer-Keldysh formalism, based on nonequilibrium-Green-function technique applied to the Landauer setup. Due to its fantastic properties, such as single Dirac cone, momentum-spin locking, and so on, the topological insulator has been regarded as one of the new generation candidates for spintronics devices and quantum computer. It is believed that electron transport along the edge of $2D$ or on the surface of $3D$ can not be backscattered even with non-magnetic impurity. Although this phenomenon is protected by time reversal symmetry, some analyses find that bound states are formed and open a band gap to allow backscattering. The contradiction would be studied by the powerful Landauer-Keldysh formalism. Whether periodic-alternating electrodes could open the Dirac point of the topological insulator or not is another interesting issue. There are experiments showing that the magnetic doping can open the Dirac point but the doping is irreversible, instead of electric field which is tuned externally and reversible. The combination of the Landauer-Keldysh formalism and Floquet theory facilitates the transport phenomena under the electric field periodically. These results would give us more understanding about topological insulator.