Topological materials and their applications

Topology is a general concept that classifies objects based on their properties that remain under continuous deformation, which is quantified by topological invariants. A common example is the number of holes in geometrical objects, which distinguishes an orange (an object with no hole) from a donut (an object with a hole). In condensed matter physics, the geometrical object is replaced by the electron’s wavefunction. Topological classification of materials has extended our understanding of a wide variety of electronic, superconducting, and magnetic phases of matter, which can lead to new technologies. In this talk, I will discuss the properties of topological materials and their applications particularly in quantum computing and spintronics.

Topological superconductors host Majorana bound states at their boundaries. In 1D topological superconductors, discrete states at zero energy (Majorana zero modes) appear at the ends of the 1D systems, which can be used to realize a topological quantum computer. Focus will be on Majorana zero modes in superconductor-semiconductor hybrid systems. In the later part, I will talk about applications in spintronics. Surface states of topological insulators are characterized by helical spin textures in momentum space. The inherent “spin-momentum locking” makes these materials promising for spintronic device applications. Experiments that reveal highly efficient spin-charge conversion will be presented.

Host Yoonseok Lee