Dr Musa Hussien was awarded his PhD for research he did on the modelling of quantum phase transitions in Dirac materials, which could drive the development of next-generation technologies, including spintronics and quantum computing.

Hussien arrived in South Africa in 2019 from his home country of Sudan, where he completed an undergraduate degree in Physics with distinction and first-class honours at the Omdurman Islamic University in 2014. He was taught there by UKZN alumnus Professor Elhadi Arbab, going on to complete his Master’s degree in Physics under the supervision of Professor Abdelnabi Ali at the Sudan University of Science and Technology in 2016.

Initially wanting to be a chemist because of his love of the discipline, his studies in physics and his realisation of the applications of the subject piqued his interest and Hussien was drawn to how physics could help society and its development. During his master’s studies, he conducted computational work on condensed matter physics that cemented his future research direction.

Driven to explore other institutions for his PhD research to enrich and diversify his academic experience, Hussien studied at the Omdurman Islamic University and received funding from the Sudanese government. The advent of the COVID-19 pandemic, however, put this funding on pause for two years resulting in Hussien returning to Sudan until 2021. Despite this setback he persevered, believing that obstacles contribute to developing strength and inspiration to think differently.

Returning to Pietermaritzburg, he was able to work on Dirac materials, a class that includes materials such as graphene, Weyl semimetals, and topological insulators that have unique electronic signatures and exhibit topological properties that distinguish them from conventional metals and semiconductors.

He was driven to understand quantum phase transitions in Dirac materials and studied the behaviour of electrons when the system was perturbed.

The Dirac cones in these materials possess electronic properties that lead to exotic phenomena, including the anomalous Quantum Hall effect, the Klein paradox, and topological phases of matter. With external parameters like an electric field or pressure change, materials undergo quantum phase transitions driven by quantum fluctuations that can result in the emergence of new phases of matter with different electronic, magnetic or topological properties.

‘Understanding quantum phase transitions in Dirac materials is important because they can lead to the discovery of new states of matter and the development of novel electronic devices,’ said Hussien.

He said that modelling these transitions in Dirac materials could help researchers understand the behaviour of these materials and develop new ways to manipulate their electronic properties for use in quantum computing, spintronics, and non-volatile memory devices, among others.

Supervised by Professor Aniekan Ukpong, Hussien found that his time at UKZN helped him form a strong research network through participation in workshops and conferences – as a PhD candidate, he was able to attend academic meetings on machine learning and theoretical physics in Rwanda and Switzerland respectively.

The results of two of his strategies, involving renormalisation of the electronic band structure of Tantalum Arsenide on a Graphene sheet, and applying various phenomenological fields (such as magnetic exchange field, electric field, and Rashba spin-orbit coupling) to obtain a topological phase diagram, showed that applying two external fields alongside the honeycomb lattice could induce transitions between trivial and topological electronic phases and revealed a first-order quantum phase transition from a half metal to full metal transport phase induced by an electric field.

Hussien published aspects of his results in two special issues of the high-impact journal Nanomaterials.

Having achieved the dream of a PhD, Hussien hopes to find a space where academia and industry meet to pursue a profession, particularly where he can continue investigating the area of machine learning. He is driven to continue producing high-quality research and is currently on the lookout for postdoctoral research positions to share the knowledge he gained with up-and-coming researchers in theoretical and computational condensed matter physics.

Hussien thanked his family in Sudan, friends, colleagues and lecturers, especially Arbab. He also thanked Ukpong, saying he could not give him enough credit. Finally, he thanked God.

Words: Christine Cuénod

Photograph: Supplied