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Séminaire « Nanoélectronique Quantique »

Mardi 1er octobre à 15 h,
salle Remy Lemaire, K223

Orateur : John R. Kirtley, Stanford University, California and Nanosciences Foundation, Grenoble
"Scanning SQUID Microscopy of Topological Insulators"


Topological insulators (TI) have electronic band structures such that although the bulk is insulating, the surface has topologically protected surface conduction channels. These materials have been predicted to have a number of interesting properties, including quantized conduction in edge channels, and unusual current-phase characteristics in superconducting-TI-superconducting Josephson tunnel junctions. We have used scanning SQUID microscopy to image the currents in Hall bars made from HgCdTe quantum wells.[1] These images show that the conduction is predominantly along the edges when the Fermi level is in the bulk band gap, but that there is also a regime in which the edge channels coexist with the conducting bulk. We have also used a scanning SQUID microscope to determine the current-phase characteristic in Josephson junctions composed of the topological insulator Bi2Se3 in superconducting aluminum rings. These junctions exhibit a conventional, nearly sinusoidal 2-pi periodic current-phase relation.

[1] K.C. Nowack et al., Nature Materials 12, 787 (2013)
[2] I. Sochinikov et al., Nano Letters 13, 3086 (2013)

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