Nanoscale Studies of Topological Insulators

Harvard University, Cambridge MA

Investigators

Abstract

Technical Abstract Topological insulators are a newly discovered class of materials with insulating bulk states and metallic surface states. The surface states are chiral and spin-polarized, and therefore protected from backscattering. The spin structure and topological nature of the surface states in these materials make them a novel playground for studying magnetism, topological superconductivity and exotic particles on the one hand, and enabling dissipationless spin transport and topological quantum computing on the other. This award will support low temperature scanning tunneling microscopy (STM) and spectroscopy (STS) studies on topological insulators (Bi2X3 class). The spin texture of the topological surface states will be studied using a sub-Kelvin STM and spin-polarized STM in conjunction with two-axis high-field magnets. Quasiparticle interference, an established STS technique, will be used to determine physical quantities of interest, e.g. the Fermi velocity and g-factor of surface states. Bulk and surface doping with magnetic impurities will be used to study the interplay of these surface states with magnetism. Bulk intercalation and epitaxial film growth will be used to look for topological interactions with superconductivity. The award will support the education and training of two graduate students and will create a rich intellectual environment through collaborations with theory and complementary experimental techniques. ************************************************** Non-Technical Abstract Every few years a new class of materials is discovered and takes the scientific world by storm with novel physics and technological promise. In 2009, the discovery of topological insulators created one such ripple. A topological insulator (TI) is an electrical insulator in its interior. On its surface, however, it is not only a metal with charges free to move, but a special metal where those charges are prevented from backscattering, removing the primary source of dissipation and heating in microelectronics. These properties make TIs promising candidates for enabling a couple of futuristic technologies: spintronics, a very low power replacement for conventional electronics, and quantum computing, a transformational method of rapidly solving computationally intensive problems. This award will support studies of topological insulators using scanning tunneling microscopes - instruments that map electronic behavior at the atomic scale. Surface-sensitive probes like these are ideally suited to study the novel surface properties of these materials. In collaboration with theory and other experimental techniques, the path toward these and other new technologies will be assessed.