Organic Control of Topological Surface States for THz Logic

Summary

Topological Insulators are a special class of materials which exhibit a conducting surface state as a consequence of band inversion. This surface state has remarkable properties, including spin-momentum locking and near lossless transport of Dirac fermions. These materials have a wealth of applications in computing, sensing and THz communications. Topological surface states can be actively controlled through the use of organic dopants, providing a route towards low-loss, high speed electronics for communications, sensing and quantum technologies.

Objectives

The project will proceed in three stages. Firstly, hybrid materials fusing topological insulators and organic semi-conductors will be developed through collaboration with Leeds University, and analysed using the electron microscopes in the Kelvin Nano-Characterisation Centre at Glasgow and at SuperSTEM. We will establish growth processes to produce the highly insulating TI material, BiSbTe, coated with highly crystalline layers of C60, as well as organic molecules such as Cu-Pthalocyanine. In the second phase, we will analyse the surface states of these materials, looking for signatures of topological surface states and their modification by organics. In the third phase, we will pattern these materials into nano-antennae, in order to analyse the plasmonic characteristics of the surface states using electron energy loss spectroscopy.

Novelty

By the end of the project, we will have firmly established a new paradigm for engineering the surface states of topological insulators. Until now, organic semiconductors and TIs have not been integrated into a single device due to the difficulty of deposition, and could not be used to modify surface states in realistic devices. This has now been solved by the creation of the Royce Deposition System at the University of Leeds. By combining the materials expertise of Leeds with world leading electron microscopes at Glasgow, we can explore this entirely novel class of hybrid materials and develop new device concepts from them.

Alignment and Strategy

This project aims to reduce energy consumption of communication and computational infrastructure by utilising extremely low-loss transport regimes in active devices. This is achieved through the development of advanced functional materials that take advantage of novel condensed matter physics. These devices will ultimately be applied in photonic circuits and potentially in devices that integrate photonics and spintronics.

Collaborations

The project is supervised by Dr Timothy Moorsom, Lecturer in Advanced Materials and Royal Academy of Engineering Fellow, and Dr Donald MacLaren, Senior Lecturer, in the Materials and Condensed Matter Physics group. The project involves the fabrication and characterisation of topological-insulator-organic hybrid devices for plasmonic applications. They will utilise the James Watt Nanofabrication Centre cleanroom facilities as well as the Kelvin Nanocharacterisation Centre's electron microscopy equipment, developing cutting edge skills with state-of-the-art equipment. In addition to work at the University of Glasgow, they will utilise the Henry Royce Institute's multifunctional MBE, at the University of Leeds, to grow novel topological materials. There will also be opportunities to take part in collaborative experiments at national and international facilities such

as the Rutherford Appleton Laboratory, the Paul Scherrer Institute in Zurich and the ALBA synchrotron in Barcelona.