Visualizing Helical Metals on the Surface of Topological Insulators

by Prof. Ali Yazdani (Princeton University)

Tuesday 3 Apr 2012, 16:00 → 18:00 Europe/Rome

Aula Conversi (Dipartimento di Fisica - Ed. G. Marconi)

Soon after the discovery of quantum mechanics it was realized why some solids are insulating (like diamond) and others are highly conducting (like graphite), even though they could be comprised of the same element. Now, 80 years later, the concept of insulators and metals is again being fundamentally revised, with the discovery of a distinct type of insulators, which can occur because of the topology of the electronic wavefunctions at their surfaces. I will describe experiments that directly visualize these novel quantum states of matter through spectroscopic mapping with the scanning tunneling microscope (STM). These experiments show that the spin texture of these states protects them against backscattering and localization, allowing them to penetrate through barriers that stop other electronic states. I will also describe ongoing efforts focused on unraveling the physics of topological surface states and their potential applications for the realization of other exotic quantum states, such as Majorana fermions.