Olga Arroyo is defending her thesis: "Contributing to more fundamental research is also very exciting"

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Olga Arroyo is becoming a new doctor on September, 23. Her work, entitled 'Emergent states in topological and Dirac matter', has been supervised by Leonor Chino, who used to be a member of the Theory of Quantum Materials and Solid State Quantum Technologies group at the Material Science Institute of Madrid and later moved to Universidad Complutense de Madrid. "The main objective of this thesis is to explore new perspectives on topological and moiré Dirac matter", explains Arroyo. In this interview she talks about her work. 

Why did you choose ICMM for your PhD?

I was already familiar with ICMM, since I did a summer internship under the supervision of Silvia Gallego when I was a student at Universidad Autónoma de Madrid. It was a great first contact with the academic and research world. At ICMM there are both theoretical and experimental groups, which is very valuable. I also attended the course Emergence of Quantum Phases in Novel Materials after finishing my master, where I discovered the interesting research topics the members of the Theory of Quantum Materials and Solid State Quantum Technologies group work on.

How would you explain your research to a non-scientific audience?

My research focuses on some physical effects that appear at the nanoscale and that have attracted a lot of interest lately in condensed matter physics. For instance, in bilayer graphene with a small rotation angle between layers, we can find localized states and strong electron-electron interactions, superconductivity, and topological phases. Theorists and experimentalists are exploring many other two-dimensional materials in order to find similar phenomena. In my thesis, I have first studied carbon nanotubes which, for a change, are one-dimensional, but nevertheless show similar localization effects. 

Second, I have also studied diverse types of topological materials, which are systems that usually host surface or edge states that are very robust. These topological states can be tuned by playing with the symmetries of the system, such as time-reversal symmetry or crystalline symmetries. In particular, I have worked with three-dimensional semiconductors with mirror symmetry and two-dimensional semiconductors and semimetals with threefold rotational symmetry. In these materials we may find two-, one- and zero-dimensional topological states depending on the conserved symmetries.

What are the main applications of your research? Could you give us an example?

The presence of robust surface or edge states in topological materials ensures interesting applications in electron transport or spin transport (spintronics), or in the fabrication of electronic devices like transistors. Layered materials are also especially interesting since we can tune their electronic properties by stacking or rotating layers. 

On a different note, some of the topological and electronic properties I have studied are new and therefore they have not been experimentally reported yet; being able to contribute to this more fundamental research is also very exciting.

What are the lessons you had learned here? which one do you value the most?

I believe that working in team, with people from diverse backgrounds that can show you different perspectives, is very important and enriching. Since I have worked in the properties of diverse systems in my thesis, I have been able to compare different approaches, some of them more analytical-oriented and others more computational-based. The research and human environment at ICMM, as well as in the universities I have visited during my PhD, has been great.

How do you think this experience will contribute to your training and to your future?

During these years I have been very lucky to meet and collaborate with many scientists and to learn from them. I have become familiar with diverse many-body quantum materials simulation codes and learnt their advantages and disadvantages. Besides, I have acquired experience in other formalisms such as tight-binding, Green's functions, or group theory approaches, which I'm sure will be very useful for me in the future. I have also gained teaching experience at university.

What are your plans once you finish your PhD?

I will be starting a postdoctoral position at Universidad de Salamanca and continue with my research in theoretical condensed matter physics as well as learning more about quantum computing.

Why did you become a scientist? Who have been your role models?

I really enjoyed going to science museums when I was a kid. Then, I had a very good mathematics teacher at high school, which motivated me to follow the sciences itinerary. There have always been some fields in physics that have been especially exciting for me, so I am very happy I am able to learn more about those topics in my job.