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PGI-1 Seminar: Dr. Paolo Sessi

Visualizing topological states of matter and their interaction with perturbations using local probes

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03 Jun 2015 11:30
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PGI Lecture Hall

Würzburg University

Abstract:

Topological insulators are a new class of materials insulating in the bulk, but which host on their surface linearly dispersing Dirac states. Contrary to the trivial surface states usually found at surfaces in metals and semiconductors, topological states cannot be destroyed by the presence of defects and adsorbates as long as time-reversal symmetry is preserved. Furthermore, the strong spin-orbit coupling inherent to these systems perpendicularly locks the spin to the momentum, resulting in a chiral spin texture which give them unconventional properties such as forbidden backscattering and results in spin currents intrinsically tied to charge currents. This makes topological insulators attractive materials for spintronics and magneto-electric applications as well as a promising platform to explore unconventional states of matter.
Since these properties manifest at boundaries, scanning probe techniques are ideal tools to visualize them with both high spatial and energy resolution.
In my talk, I will first describe experiments that, through quantum interference, allow not only to visualize the presence of these unconventional boundary states, but also to demonstrate some of their unusual properties.
I will then discuss more recent efforts focused on their controlled manipulation, which is required to make them useful for new technologies and can be achieved by direct coupling to well defined external perturbations. In particular, I will show how local magnetic order can be established at very dilute concentrations using 3d adatoms and how the creation of charge puddles associated with their random distribution can be avoided by embedding the magnetic moments into molecules to create self-assembled networks of different symmetries.

Contact

Prof. Dr. Stefan Blügel
Phone: +49 2461 61-4249
Fax: +49 2461 61-2850
email: s.bluegel@fz-juelich.de

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