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Thanh Nguyen has a habit of breaking down barriers. Take languages as an example: Nguyen, a third-year nuclear science and engineering (NSE) doctoral student, wanted to “connect with other people and cultures” for his work and social life, he says, so he learned Vietnamese, French, German and Russian, and is currently taking an MIT course in Mandarin. But this desire to overcome obstacles is really evident in his research, where Nguyen tries to unravel the secrets of a new branch of physics in full swing.
“My thesis focuses on neutron scattering on topological semi-metals, which were only discovered experimentally in 2015,” he says. “They have very special properties, but since they’re so new, there are a lot of unknowns, and neutrons offer a unique perspective to probe their properties to a new level of clarity.
Topological materials do not fit perfectly into the conventional categories of substances found in everyday life. They were first materialized in the 1980s, but did not become practical until the mid-2000s with a deep understanding of topology, which is concerned with geometric objects whose properties remain the same even when the objects undergo extreme strain. Even more recently, researchers have experimentally discovered topological materials, using the tools of quantum physics.
In this field, topological semi-metals, which share the qualities of metals and semiconductors, are of particular interest to Nguyen. “They offer high levels of thermal and electrical conductivity and inherent robustness, which makes them very promising for applications in microelectronics, energy conversions and quantum computing,” he says.
Intrigued by the possibilities that could emerge from such “unconventional physics”, Nguyen pursues two related but distinct fields of research: “On the one hand, I try to identify and then synthesize new robust topological semi-metals, and on the other hand, I want to detect new fundamental physics with neutrons and design more new devices. “
On a quick search trail
Achieving these goals over the next few years may seem like a tall order. But at MIT, Nguyen seized every opportunity to master the specialized techniques needed to conduct large-scale experiments with topological materials and achieve results. Guided by his advisor, Mingda Li, assistant professor Norman C Rasmussen and director of the Quantum Matter Group at NSE, Nguyen was able to delve into important research even before setting foot on campus.
“In the summer, before I joined the group, Mingda sent me on a trip to the Argonne National Laboratory for a very fun experiment that used synchrotron X-ray scattering to characterize topological materials,” recalls Nguyen. “Learning the techniques fascinated me in the field and I started to see my future.”
During his first two years of graduate school, he participated in four studies, as a lead author in three journal articles. In a remarkable project, described earlier this year in Physical examination letters, Nguyen and his fellow researchers from the Quantum Matter Group have demonstrated, through experiments carried out in three national laboratories, unexpected phenomena involving the way in which electrons move in a topological semi-metal, tantalum phosphide (TaP).
“These materials are inherently resistant to disturbances such as heat and damage, and can conduct electricity with a certain level of robustness,” explains Nguyen. “With such rugged properties, some materials can conduct electricity better than better metals and, under certain circumstances, superconductors – which is an improvement over current generation materials.
This discovery opens the door to topological quantum computing. Current quantum computing systems, where the elementary units of computation are qubits that perform ultra-fast computations, require superconducting materials that only work in extremely cold conditions. Fluctuations in heat can throw any of these systems out of balance.
“The inherent properties of materials like TaP could form the basis of future qubits,” Nguyen explains. He plans to synthesize TaP and other topological semi-metals – a process involving the delicate cultivation of these crystal structures – and then characterize their structural and exciting properties using neutron and x-ray beam technology, which probe these materials at the atomic level. This would allow him to identify and deploy the right materials for specific applications.
“My goal is to create programmable artificial structured topological materials, which can be directly applied as a quantum computer,” Nguyen explains. “With infinitely better heat management, these quantum computing systems and devices could prove to be incredibly energy efficient.”
Physics for the environment
Energy efficiency and its benefits have long been of concern to Nguyen. A native of Montreal, Quebec, with aptitudes in mathematics and physics and a concern for climate change, he devoted his final year of high school to environmental studies. “I worked on a Montreal initiative to reduce heat islands in the city by creating more city parks,” he says. “Climate change mattered to me and I wanted to have an impact.”
At McGill University, he majored in physics. “I became fascinated with the issues on the ground, but I also felt that I could eventually apply what I learned to achieve my environmental goals,” he says.
In both classes and research, Nguyen immersed himself in different areas of physics. He worked for two years in a high-energy physics lab manufacturing neutrino detectors, as part of a much larger collaboration to verify the Standard Model. In the fall of his final year at McGill, Nguyen’s interest turned to condensed matter studies. “I really enjoyed the interplay between physics and chemistry in this area, and I especially enjoyed exploring questions of superconductivity, which seemed to have many important applications,” he says. That spring, seeking to add useful skills to his research repertoire, he worked at Chalk River Laboratories in Ontario, where he learned to characterize materials using neutron spectroscopes and others. tools.
These academic and practical experiences propelled Nguyen to his current graduate program. “Mingda Li came up with an interesting research plan, and although I didn’t know much about topological materials, I knew they had been recently discovered and I was delighted to enter the field,” he says. he.
Man with a plan
Nguyen has mapped out the final years of his doctoral program and they will prove to be demanding. “Topological semi-metals are difficult to work with,” he says. “We don’t yet know the optimal conditions to synthesize them, and we need to make these crystals, which are at the micrometer scale, in quantities large enough to allow testing.”
With the right materials in hand, he hopes to develop “a qubit structure that is not so vulnerable to disturbance, rapidly advancing the field of quantum computing, so the calculations that now take years may only require a few. minutes or seconds, ”he said. “Significantly higher computing speeds could have huge impacts on issues such as climate, health, or finance that have significant ramifications for society.” If his research on topological materials “benefits the planet or improves the way people live,” says Nguyen, “I would be totally happy.”
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