Lukas Muechler, assistant professor of chemistry and of physics, discusses how his research group is working on bridging chemistry and physics in the field of quantum materials by developing new theoretical concepts and tools that will benefit future technologies.
Kathryn: You joined the Penn State Chemistry faculty as an assistant professor in August of 2021. How has it been working in the department over the last two years? What do you enjoy most about it?
Lukas: I have really enjoyed my time here so far. I arrived towards the end of the Covid restrictions and was lucky enough to be in-person for everything. I have felt very supported and included here, which is important to me. Our monthly launch committee meetings and faculty mentors have helped me in particular. The most fun has been building up my group and starting our own independent research. I enjoy working with them and am very fortunate to have such great group members. We are now preparing the first set of papers to be published!
Kathryn: How did the research you were doing as a postdoc at CCQ (Flatiron Institute Center for Computational Quantum Physics) impact what you wanted to focus on in your own research lab?
Lukas: The CCQ is a very interesting project because every postdoc is essentially independent, and they leave it to you to who you work and collaborate with. This helped me develop my own set of ideas and projects that I wanted to work on. I was also fortunate enough to be able to organize a conference at the CCQ that focused only on young researchers, i.e., pre tenure, which allowed me to build a network. I have always been a very collaborative person and so I really enjoyed the freedom and possibilities I had in my postdoc. Since the CCQ had a diverse background of researchers, I was exposed to many areas of theoretical physics and chemistry that helped shape the research of my own group. I learned a lot about technical implementations of programs such as PySCF (Python-based Simulations of Chemistry Framework) or TRIQS (Toolbox for Research on Interacting Quantum Systems), which I still use today.
Kathryn: Your research group works with quantum materials at the interface of chemistry and physics. Can you explain the relationship between chemistry and physics and why it is important to understand their connection in the field of quantum materials?
Lukas: What often makes communication between chemists and physicists challenging is their different perceptions of what is considered fundamental. For instance, chemists might view a property inherent to certain crystal structures, while physicists look for the underlying mechanisms, often captured by abstract models. These different approaches can frequently appear irreconcilable at first glance. However, chemistry isn't merely applied physics, nor is physics just applied math. I believe that both disciplines have their unique language and methods tailored to their core interests.
What makes this interesting for me is that I strongly believe modern challenges at the interface of these fields demand a fusion of methods and ideas from both chemistry and physics. Recent theories of topological phases I have worked on have been influenced by concepts developed in both disciplines, and they include considerations of crystal structures and chemical bonding as well as more abstract mathematical concepts.
In my own research, I aim to bridge these differences. Can we discover the unspoken assumptions behind how chemists think and reformulate them in a language combining chemical ideas with a more fundamental theory? Or reinterpret physics concepts in a chemical language that's more accessible to chemists? By blending the insights of both fields, we're better equipped to understand the complex properties of quantum materials, potentially leading to novel and groundbreaking discoveries.
Kathryn: Tell us about some projects your group members are currently working on. What are topological materials and why is your group so interested in them?
Lukas: My lab is currently pursuing two main research thrusts: The first is to understand how we can better design two-dimensional materials that can be used as so-called single photon emitters (SPE). SPEs will likely play a major role in future technologies, such quantum communication networks and encryption, due to the special nature of the photons that are emitted by these materials. What is less clear, however, is how to make materials that have the right properties to be implemented with current technologies like optical fiber networks and so on. We are currently collaborating with the Robinson Lab at Penn State in trying to find and optimize the properties of materials such as MoS2 in presence of lanthanide atom defects, which have been predicted to be ideal SPE. However, not much is known about the chemistry of these defects, and our atomistic simulations will help us to understand these materials better.
The second thrust is concerned with employing the mathematical language of topology to comprehend and predict reaction dynamics. As society seeks alternatives to oil and faces the challenges of climate change, innovative chemical synthesis methods are essential. To address this challenge, we are developing a fundamentally novel approach for exploring the quantum mechanical principles of chemical reactivity by leveraging recent breakthroughs in the field of topological physics. In this context, topology refers to the mathematical study of the properties of objects that remain unchanged under continuous deformations. It's been a game-changer in understanding electronic states in crystalline materials, leading to the discovery of new quantum states like topological insulators which earned a Nobel Prize in Physics in 2016. During my graduate and post-doctoral research, I worked extensively on these concepts, and we are now in the process of applying them and tools to an area of chemistry.
At first glance, topological materials and chemical reactions might seem unrelated, but the mathematics underlying both share intriguing connections. While it's an unproven method, we've found instances where this approach has worked remarkably well, which I find extremely encouraging.
Kathryn: What challenges have your group faced when using theoretical approaches and realistic models on materials that do not yet exist or are in the process of being discovered?
Lukas: When delving into unexplored territories in research, challenges are inevitable, particularly when no established methods exist to guide our way. This is the scenario we often find ourselves in, especially with our work on using topological methods for reaction chemistry. As we push the boundaries of current understanding, we encounter situations where there's no existing literature to refer to. This lack of precedent means we must deeply understand every aspect of what we are working on and rigorously verify all our derivations and formulas. Fortunately, we are not alone in these explorations, as we actively collaborate with groups from the Penn State physics department on these questions.
Kathryn: Where do you see the future of quantum materials headed with respect to new technologies?
Lukas: I think quantum materials could potentially revolutionize technology as it has been predicted many times. However, these predictions have not become reality yet because the materials and devices have not yet been made or discovered. I think this is a very exciting time for us because it highlights the importance of basic research, especially a holistic approach that requires chemists and physicists to work together. Penn State is a leader in this area with very strong materials, engineering, chemistry and physics departments as well as the MRSEC and NSF 2D Materials Center.
Kathryn: Lastly, where do you hope to see your lab in the next few years? Have you set yourself and your group any specific goals?
Lukas: It would be very nice to be able to show that our ideas about topology and chemistry are correct. I hope that our lab can take on a leadership role in this field and that we will be able to convince other groups to follow us down this rabbit hole. Similarly, I am very optimistic about our research on SPEs. We have some exciting ideas on how to make our theoretical predictions more accurate and I can’t wait to try them out. As far as the group is concerned, my main goal is to establish the right group culture and knowledge base for a long-term research program. For me, it is very important to be able to discuss and collaborate with my group members and I want to encourage them to go out there and explore.