Frontier Research Institute for Interdisciplinary Sciences
Tohoku University

Topology is a mathematical concept for classifying geometry of objects. For example, a donut cannot be transformed to a pancake continuously – without cutting the ring of it. Application of this mathematical concept to solid state physics leads to the discovery of a new class of materials - topological materials. Unlike usual insulators, metal, or semiconductors, their overall properties do not depend on detailed characteristics of materials but determined from symmetries of lattices. For example, a topological insulator – a class member of topological materials – hosts high mobility metallic states on its surface, even if its bulk part is insulating. This property is universal and protected by time reversal and inversion symmetries. Insensitivity to details of material parameters is advantageous for device applications.

I had been working in Massachusetts Institute of Technology on synthesis and characterization of topological thin film materials to understand the effect of thin film morphology on their physical properties. With this expertize, I came to FRIS to develop mesoscopic topological electronic devices with functionalities absent in conventional devices. In particular, junctions between topological insulators and superconductors host quasiparticles which act as an elementary particle “Majorana fermion.” Solid state devices in which one can coherently manipulate Majorana fermions are promising platforms for quantum computation resistant to computation errors.