Dai-Nam Le is a postdoctoral researcher at the University of South Florida developing theoretical tools to predict and control nanoscale quantum forces, including quantum friction and Casimir interactions, to enable next-generation nanodevices. In this Postdoc Portrait interview, he shares how the smallest forces can have the largest impact in the quantum space.
Uncovering Fundamental Nanoscale Quantum Forces
Q | What scientific problem are you trying to solve?
I study how things rub, stick, and pull on each other at the smallest scales, where just a few nanometers separate one material from another and the usual rules of classical physics give way to quantum mechanics. At these scales, two main effects take over. The first is quantum friction, which is the energy lost when atom-scale surfaces slide past each other. Unlike the friction we see in daily life, this kind relies on quantum tunneling, where particles can pass through barriers they normally couldn't cross. The second is the Casimir force, a surprising pull or push between objects that comes from the fluctuations of empty space. These effects together control how tiny machines move, how layered materials stick, and how quantum devices work. My goal is to create the theoretical tools needed to predict and eventually control these effects in real materials, so that future nanodevices and quantum technologies can be designed with these subtle quantum forces in mind, instead of working against them.
Q | What drew you to physics?
I was first drawn to physics by the unusual beauty of its mathematics. As a student in Vietnam, I worked on a problem about magnetic monopoles in nine dimensions. It was an abstract puzzle that most physicists never see, but its elegance showed me that mathematical structures can hide deep physical truths. That belief has stayed with me. Over time, I shifted from purely mathematical problems to physics with real-world impact, starting with two-dimensional materials and Dirac systems, and now focusing on friction and Casimir forces. What I love about these topics is that they sit where two worlds meet. On one side, they are subtle predictions of quantum theory, coming from the fluctuating vacuum of empty space. On the other, they directly affect how real devices work at the nanoscale. Few research questions offer both deep theory and immediate practical value, and that combination keeps me interested.
Controlling Dissipation and Designing Quantum Technologies
Q | What’s one thing you learned about quantum friction that you didn’t expect?
The biggest surprise has been how often the things we think are minor end up driving the whole phenomenon. When I started studying quantum friction, I thought it would look like classical friction with small quantum changes. Instead, quantum tunneling completely changed the dynamics, creating motion that doesn't exist in classical physics. I saw the same thing in my work on Casimir forces. The Casimir effect was first calculated assuming only electrons mattered, but in piezoelectric materials, I found that lattice vibrations, the gentle movements of atoms in a crystal, can be so strong they actually reverse the force, turning attraction into repulsion. In other words, the parts we thought were just background turned out to be the main players. This has taught me to be very careful with words like "negligible." At the nanoscale, the things we think are unimportant often decide what really happens.
Q | If your research succeeds, what could it change for science or society?
We will be able to predict and eventually design how matter behaves at the smallest scales, where quantum effects control sticking, friction, and heat flow. This could have real impacts across science and technology. In nanotechnology, it could help engineers build tiny machines that use Casimir and frictional forces to their advantage. In quantum computing, where quantum bits are very sensitive to their surroundings, understanding these forces could help reduce unwanted energy loss. In materials science, it could help create two-dimensional materials with special properties for sensors, energy harvesting, and electronics. More broadly, this work helps connect fundamental physics with engineering, showing that questions once seen as abstract can lead to tools that shape future technologies. I find it meaningful that curiosity-driven theory can quietly enable tomorrow's devices.
Q | What question are you most excited to answer next?
I want to know whether we can turn quantum friction on and off at will. Friction at the nanoscale isn't the boring, unavoidable force we know from daily life. Instead, it's a quantum effect shaped by tunneling, vibrations, and zero-point energy. My recent work has shown how surprising and complex this area can be, but the bigger challenge is ahead: Can we use electric or magnetic fields, strain, or special materials to control dissipation like we control electric currents? If we can, we might see ultra-low-friction nanomachines, more accurate scanning probes, and new ways to study dissipation in quantum systems. What excites me most is that this question brings together both parts of my research—friction and Casimir interactions—into one project. It's the kind of question where a theory could directly guide experiments, and that teamwork is what I enjoy most about physics.
Responses have been edited for length and clarity.
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