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CM-AMO Seminar<br>Making and Investigating Topologically Nontrivial Compounds<br><b>Speaker: Dr. Nicholas Butch (Lawrence Livermore National Laboratory, Condensed Matter and Materials Division)</br></b>

Tuesday, December 13, 2011
12:00 AM
335 West Hall

Speaker: Dr. Nicholas Butch (Lawrence Livermore National Laboratory, Condensed Matter and Materials Division)

Theoretically, three dimensional topological insulators are bulk insulators with two dimensional metallic surface states that are spin chiral. While the existence of the novel surface states has been confirmed, it has proven challenging to isolate signatures of electrical transport from the surface states; this will be necessary to realize potential applications of these materials. I will describe the synthesis and characterization of high quality single crystals of the most intensely studied topological insulator material Bi2Se3, which have exceptionally low bulk carrier density and high mobility. Unambiguously identifying surface transport in these very clean samples remains difficult, but I will touch on some promising approaches to studying the novel physics in this material. Also, I will discuss the recent discovery of superconductivity in the semimetal YPtBi, whose band structure is predicted to be topologically nontrivial. This intriguing superconducting state has an unusual mix of properties: a record low normal state carrier density (1018 cm 3), lack of crystalline inversion symmetry, and strong band inversion.