Illustration of the emergence of topological electric charges at the corners of NaCl

Space and locality: an interview with Adrian Po

15 May 2024

Dr Adrian Po was the winner of a Croucher Tak Wah Mak Innovation Award in 2023. Croucher News caught up with him recently and found out more about his work—and why theoretical physicists don’t just drop in on each other at work.

Po is currently Hari Harilela Assistant Professor of Physics at Hong Kong University of Science and Technology. His career in science started with a BSc in physics at Chinese University of Hong Kong. He then started his PhD at UC Berkeley and finished it at Harvard before carrying out postdoc research at MIT. He told us: “I might not have noticed that at the time, but now, when I think back, I realise that all these experiences really shape how you think and how you act.”

One thing he learnt during that time was that everyone is fallible—even the very best minds. “I’ve had the privilege to talk to and interact with many different physicists who are really well-known, even maybe Nobel Laureates. These people are really smart. But I think maybe the most important thing is to realise that they are also human. And even extremely smart people can make mistakes. It’s good for me to see that even if I’m not as smart as they are, at least I share some commonality when it comes to making mistakes.”

Po is wary of generalising about the difference between institutions in California and the East Coast, but he did find students more relaxed on the West Coast. “Though maybe that’s because they were at the beginning of their PhD studies and didn’t feel the pressure that I saw later on the East Coast, which came when all my cohort were looking for jobs,” he added.

Po joined HKUST in 2021. He already knew scientists who were working there, and, above all, he knew the university had a critical mass of people working in his field. “HKUST had thought very strategically when they set up their physics department,” he told us, ”and focused on a few areas in order to make sure they were well resourced. Condensed-matter physics is one of them.”

The Innovation Award will give Po a chance to explore ideas that other funding schemes might find quite risky in terms of a successful outcome. “I understand that the award is unusual in the sense that they really reward you for trying to do something innovative, as the name suggests. And that’s not very common in the space of scientific funding. People like to hear about crazy ideas, but maybe not to fund them. And that’s reasonable. But Croucher Foundation really doesn’t mind if you propose something which is quite different or a rather risky kind of project.”

Po’s research will look at space and locality in new ways. “If you imagine two points, A and B, you expect them to have some influence on one another if they are near each other. And if they are far away from each other, you don’t expect to see any influence. However, in certain quantum systems, we see that electrons far apart can behave in a correlated manner. This suggests these electrons might be effectively closer to each other than we thought.”

If you imagine two points, A and B, you expect them to have some influence on one another if they are near each other.

“So the research I am doing starts by admitting that the physical distance between point A and point B may not be the correct starting point for understanding the electronic behaviours in such quantum systems. And it is in some additional, maybe hidden, or extra dimension or space that electrons at points A and B may be secretly closer to each other. If this is so, we are trying to systematically work out what the structure might be.”

Although Po and his team use computers for certain calculations, most of the tools he uses are pens, paper, and a whiteboard. “Other key resources are coffee and people,” he added. “You need people to bounce ideas off,” he said. “It’s not only about their skills or knowledge; it is the interaction that really helps. Sometimes you may not notice things just because you’re not looking from the right angle. Discussing with people who know a lot will certainly help in arriving at new perspectives, and even talking to people who know less can be fruitful.”

Dr Adrian Po in his office at HKUST

When we asked about the resourcing of his work, Po explained that physics is divided between theoretical and experimental sides. Whereas the experimenters needed to invest a lot in equipment to do science, the main investment for theorists like himself was in people. “We want top talent,” he said. “And in Hong Kong, we’re lucky to have a great talent pool in Mainland China, which really helps.”

Sometimes, when he hits up against a major challenge in his work, Po will take a walk to help think the problem through. “At MIT, you could walk for hours through the corridors, sheltered from the harsh Boston weather,” he told us. “And at HKUST, we have a great location.” But most of the time, he does his thinking in his room. And it seems he can do this without too many interruptions. “The other people in the department are physicists too,” he explained. “So we tend to leave each other with plenty of thinking time, which we all need.”

Scientists are often asked about the practical implications of their work. When we asked Po this question, he began by explaining that the current digital revolution is powered by semiconductors, which were the subject of research by theorists in his area 50 to 70 years ago. “So, who knows?” he speculated. “Maybe what we’re working on now will lead to the basic technologies that’ll be used 50 years from now.”

Dr Adrian Po received a Croucher Fellowship (2018) and Croucher Tak Wah Mak Innovation Award (2023). To view his Croucher profile click here