Prof. Laurens W. Molenkamp: "HgTe as a Topological Insulator"
| Termin |
Donnerstag, 18. Juni 2015, 17.15 - 18.30 Uhr |
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| Veranstaltungsart | Vorlesung/Vortrag |
| Einrichtung | Naturwissenschaftliche Fakultät II |
| Veranstalter | Institut für Physik, SFB 762 |
| Veranstaltungsort | Gustav-Mie-Hörsaal |
| Straße | Theodor-Lieser-Str. 9 |
| PLZ/Ort | 06120 Halle (Saale) |
| Ansprechpartner | Michael Strauch |
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| Telefon | 345-5525449 |
| michael.strauch@physik.uni-halle.de |
Beschreibung
Prof. Laurens W. Molenkamp von der Universität Würzburg referiert zum Thema: "HgTe as a Topological Insulator".
HgTe is a zincblende-type semiconductor with an inverted band structure. While the bulk material is a semimetal, low-ering the crystalline symmetry opens up a gap, turning the compound into a topological insulator.
The most straightforward way to do so is by growing a quantum well with (Hg,Cd)Te barriers. Such structures ex-hibit the quantum spin Hall effect, where a pair of spin po-larized helical edge channels develops when the bulk of the material is insulating. Our transport data provide very direct evidence for the existence of this third quantum Hall effect, which now is seen as the prime manifestation of a 2-dimensional topo-logical insulator. To turn the material into a 3-dimensional topological insula-tor, we utilize growth induced strain in relatively thick (ca. 100 nm) HgTe epitaxial layers. The high electronic quality of such layers allows a direct observation of the quantum Hall effect of the 2-dimensional topological surface states. Due to the screening properties of Dirac fer-mions, these states turn out to be decoupled from the bulk for a very wide range of densities. This allows us to in-duce a supercurrent in the surface states by contacting these structures with Nb electrodes. AC investigations indicate that the induced superconductivity is strongly influ-enced by the helical character of the charge carriers.
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| Webseite | http://wcms.itz.uni-halle.de/download.php?down=38388&elem=2887305 |
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