Center for Correlated Electron Systems

Seminar

Epitaxy of topological insulators and scalable Majorana networks

April 25, 2018l Hit 608
Date : March 19, 2018 16:00 ~ 17:00
Speaker : Dr. Joon Sue Lee(University of California)
Location : Bldg. 19, Rm. 210

Advances in material science play an important role in the research field of topological states of matter and their applications. In this talk, I will focus on epitaxial synthesis of single-crystalline materials and heterostructures with clean interfaces for studies of two different topological states: topological insulators (TIs) and topological superconducting phases that host Majorana zero modes.
In the first part, I will present molecular beam epitaxy (MBE) of Bi and Sb chalcogenides TIs on various substrates and experiments utilizing the TIs and TI-based heterostructures. The TI surface states are inherently spin-polarized, which can be detected by spin-resolved angle-resolved photoemission spectroscopy and by an electrical method of potentiometric measurement. In TI/ferromagnet hybrid systems, efficient spin-charge conversion has been demonstrated by spin-transfer torque, spin pumping, and unidirectional magnetoresistance measurements, showing that TIs have great potential for spintronic applications.
In the second part, recent progresses in the field of Majorana-based topological quantum bits will be presented. Quantized Majorana zero-base conductance peak has been achieved based on an improvement of the superconductor-semiconductor interface by growing epitaxial Al on InSb nanowires. Now the focus of this research field is on experimental demonstration of a topological quantum bit. An immediate challenge is how to realize scalable 1D superconductor-semiconductor networks. Three approaches to overcome the challenge will be discussed: 1) synthesizing self-assembled 1D nanowire networks with superconductor islands, 2) processing nanostructures on epitaxial superconductor/two-dimensional electron gas systems, and 3) selective-area epitaxy of in-plane 1D networks with an in-situ superconductor.
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Host: Prof. Changyoung Kim