DFT-NEGF transport of topological/superconducting nanoscale qubits

Topological materials, such as topological insulators (TI) or Weyls semimetals, are a novel class of materials featuring intriguing new quantum states of matters and properties. The appearance of topologically protected states at the edges of 2D nanoribbons made of TI materials (such as stanene or bismuthene) in proximity of superconducting (SC) materials may allow for the observation of the long predicted Majorana Fermions. Owing to their long coherence time, Majorana states in TI are considered as potential candidates to build quantum bits (qubits), the basic blocks to build a quantum computer, that are error tolerant. Topological materials can be used under certain conditions to enable spin-polarized transport, which is interesting for spintronics. Besides being used in conjunction with TI to induce Majorana Fermions, SC materials also have direct applications, like in Josephson-Junction used for quantum computing. In addition, the emergence of superconductivity in 2D materials has attracted much attention and there has been rapid development in recent years because of their fruitful physical properties, such as high transition temperature, continuous phase transition, and enhanced parallel critical magnetic field.

In this thesis, you will explore the transport properties of innovative transistors and qubits made of topological and superconducting 2D materials to study and tune their properties, using a blend of density functional theory (DFT) methods (Quantum Espresso, CP2K, OPENMX) and advanced ab-initio quantum transport (NEGF) simulations (ATOMOS) [1-4]. You will learn and benefit from the support from modeling experts in the field. The possibility to interact with experimentalists is also available at imec.

[1] Afzalian, A. Ab initio perspective of ultra-scaled CMOS from 2D-material fundamentals to dynamically doped transistors. npj 2D Mater Appl 5, 5 (2021). https://www.nature.com/articles/s41699-020-00181-1

[2] A. Afzalian, E. Akhoundi G. Gaddemane, R. Duflou and M. Houssa, "Advanced DFT–NEGF Transport Techniques for Novel 2-D Material and Device Exploration Including HfS2/WSe2 van der Waals Heterojunction TFET and WTe2/WS2 Metal/Semiconductor Contact," in IEEE Transactions on Electron Devices, vol. 68, no. 11, pp. 5372-5379, Nov. 2021, doi: 10.1109/TED.2021.3078412 (invited)

[3] E. Akhoundi, M. Houssa, A. Afzalian, The impact of electron phonon scattering on transport properties of topological insulators: A first principles quantum transport study, Solid-State Electronics (SI: LETTERS from the International Conference on Simulation of Semiconductor Processes and Devices 2022), 201, 108587 (2023). https://doi.org/10.1016/j.sse.2022.108587.

[4] E. Akhoundi, M. Houssa, A. Afzalian, The Impact of Electron Phonon Scattering, Finite Size and Lateral Electric Field on Transport Properties of Topological Insulators: A First Principles Quantum Transport Study: a first principles quantum transport study, Materials 2023, 16(4), 1603; https://doi.org/10.3390/ma16041603.

[5] Akhoundi, E., Houssa, M. & Afzalian, A. Spin-filtering properties of topological structures based on stanene and bismuthene nanoribbons with one edge magnetism. Discov Electron 1, 13 (2024). https://doi.org/10.1007/s44291-024-00019-w