Dresden 2017 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 70: Topological Insulators I (joined session with TT)

HL 70.6: Vortrag

Donnerstag, 23. März 2017, 11:30–11:45, POT 251

Topological insulator - superconductor hybrid devices — •Peter Schüffelgen, Daniel Rosenbach, Michael Schleenvoigt, Tobias W. Schmitt, Martin Lanius, Christian Weyrich, Tristan Heider, Benjamin Bennemann, Stefan Trellenkamp, Elmar Neumann, Gregor Mussler, Thomas Schäpers, and Detlev Grützmacher — Peter Grünberg Institute 9, Forschungszentrum Jülich & JARA-FIT, 52425 Jülich, Germany

3D topological insulators (TIs) possess metallic surface states with a spin-locked momentum. Therefore, in proximity to an s-wave superconductor, Majorana zero modes (MZMs) are predicted to occur at the surface of TIs. We found first signatures of 4π-periodic Josephson supercurrents in our topological Josephson junctions. The TI thin film was grown by means of molecular beam epitaxy on a Si(111) substrate and capped in-situ by a thin layer of aluminum to prevent thin film degradation and to preserve the pristine surface states during ex-situ fabrication. To increase the 4π-periodic contribution we fabricated quasi 1D Josephson junctions on pre-patterned silicon substrates. By covering the Si-111 surface partly with a thin layer of Si3N4/SiO2 we made the topological insulator grow only on the silicon surface. In this way we were able to realize 1D trenches by predefining the MESA structure before MBE growth. To further improve the quality of our hybrid devices we developed a process, which allows to deposit superconducting contacts via stencil lithography. Combining this technique with selective area growth allows to fabricate complex devices in-situ.