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Connecting chirality and spin in electronic devices

PhD ceremony:X. (Xu) Yang
When:September 18, 2020
Supervisors:prof. dr. ir. C.H. (Caspar) van der Wal, prof. dr. ir. B.J. (Bart) van Wees
Where:Academy building RUG
Faculty:Science and Engineering

Our lives have been transformed by the rapid development of the electronics industry, but that pace has recently slowed down due to fundamental limits of conventional silicon-based technologies. A promising candidate for next-generation electronics is spintronics. It uses the magnetic property of electrons, the spin, in addition to their conventionally used electrical charge, to process digital information.

A challenge for spintronics is to efficiently convert between spin and charge signals, which currently relies on bulk properties of magnetic materials. Recent research found an alternative approach to this — using chiral molecules. These are molecules whose shape is not mirror-symmetric, so that they cannot be made to exactly overlap with their own mirror image. Their spin–charge conversion is termed chirality-induced spin selectivity (CISS), and has been reported in various experiments involving spintronic devices. However, fundamental understanding of the observed signals has been lacking, and the underlying mechanism of CISS still remains unclear.

This thesis focuses on the manifestations of CISS in spintronic devices. Theoretically, it answers fundamental questions of how and when CISS can generate spintronic signals, how such signals can be detected, and what these signals imply about the chiral molecules. Experimentally, this thesis explores phenomena in electronic devices that are introduced by chiral solid-state and bio-organic materials. The results presented in this thesis not only provide operation principles and design guidelines for CISS-based spintronic devices, but also shed light on the fundamental link between spin and the chirality of molecules and materials.

See also: Theoretical model may help solve molecular mystery