Alumni

2014

HAYATO IKUMI

Time evolution of the electronic wave packets in weak topological insulators

In recent years, materials called topological insulator have received a lot of attention. They have metal states on surfaces, but insulator states inside the system. The surface states on weak topological insulators are said to be weak against impurities. In the bachelor thesis, I studied time evolution of electronic wave packets by using computer simulation in weak topological insulators. As a result, when the strength of impurity is small, I found the electric currents almost flowing on the surfaces. Furthermore, they flow more quickly than those in metals, strong topological insulators, and ordinary insulators.

Snapshot of the time evolution of the electronic wave packets without impurities (left) in weak topological insulator, (middle) in strong topological insulator, (right) in ordinary insulator. Size of the sample is 20 × 20 × 20, time is 12.5.

Snapshot of the time evolution of the electronic wave packets with impurities (left) in weak topological insulator, (middle) in strong topological insulator, (right) in ordinary insulator. Size of the sample is 20 × 20 × 20, time is 13.0.