Seminar: Imaging the surface states of a strongly correlated topological insulator

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Event Details

24 August 2017 at 2:00 pm – 24 August 2017 at 3:00 pm
Large seminar room 107, Physics block 1,10 College Walk
Open to:
Engineering; Science


Hear how Harvard physicists study electron behaviour within exotic materials such as topological insulators.

The prediction and subsequent discovery of topological band insulators with robust spin-polarized surface states has launched a new subfield of physics over the last decade. In the last few years it has been recognized that when topology is combined with strong electron-electron correlations, even more interesting and potentially useful states of matter can arise, such as new topological classifications, fractionalized states, and many-body localization that preserves the topology of the insulating state against thermal destruction. Here I will give a general introduction to topological materials, and show the first direct proof of a strongly correlated topological insulator. Using scanning tunneling microscopy to probe real and momentum space structure, our measurements on the heavy fermion material SmB6 reveal the evolution of the insulating gap arising from strong interactions, and a surface state with Dirac point close to the chemical potential. Our observations present the first opportunity to explore a strongly correlated topological state of matter.

Professor Jenny Hoffman is interested in how electrons behave within exotic materials. Her research team at Harvard has designed and constructed three low-temperature scanning probe microscopes to visualize and manipulate this behavior directly. Innovative techniques include quasiparticle interference imaging to extract the band structure of materials at the nanoscale, and force microscopy to trigger nanoscale electronic phase transitions. Materials of particular interest include high temperature superconductors, topological insulators, and strongly correlated vanadates, all of which present deep physics questions as well as potential for novel applications.

At FLEET Topological insulators are studied to develop electronic devices in which electrical current can flow with near-zero resistance. Unlike conventional insulators, which cannot conduct electricity, topological insulators conduct only along their boundaries, while in their centre, they behave as an insulator. The edge of a topological insulator conducts electrons in one direction only, and thus has none of the electron scattering that causes dissipation and energy loss in conventional materials.

Dianne Ruka
FLEET: ARC Centre of Excellence in Future Low-Energy Electronics Technologies