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Topological insulators are a new class of insulators in which a bulk gap for
electronic excitations is generated by strong spin-orbit coupling. These novel
materials are distinguished from ordinary insulators by the presence of
gapless metallic boundary states, akin to the chiral edge modes in quantum
Hall systems, but with helical spin textures. I will describe experiments that
visualize these novel quantum states of matter and demonstrate their unusual
properties through spectroscopic mapping with the scanning tunneling
microscope. Specifically experiments demonstrate that spin texture of these
states protect them against backscattering.[1] They also demonstrate that
unlike conventional surface states , which are localized crystalline defects,
these state can penetrate through crystalline barriers. [2] I will describe
these experiment and more ongoing efforts focused on unraveling the physics of
topological surface states.
[1] Roushan et al. Nature 460 1106 (2009). [2] Seo et al. Nature, 466 434 (2010). |
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