Exploring the statistical physics of artificial frustrated spin systems in space and time

About This Grant

Non-technical abstract Technologies that operate at the nanoscale, such as molecular machines, nanobatteries, and biological motors, function in regimes where traditional thermodynamics no longer fully applies. At these small scales and over short times, random fluctuations can temporarily allow processes that appear to violate the second law of thermodynamics. While modern theory predicts when such events can occur, experimentally observing and quantifying them in complex, interacting systems remains a major challenge. This project addresses this gap by using artificial spin systems—engineered arrays of nanoscale magnets—as highly controllable model platforms for studying nonequilibrium energy fluctuations. These systems allow direct, real-time visualization of magnetic dynamics, making it possible to track how energy flows and fluctuates as the system is driven away from equilibrium. By applying thermal and magnetic stimuli, the project will measure the frequency, magnitude, and duration of apparent second-law violations and test modern fluctuation-based theories of thermodynamics. The research combines nanofabrication, advanced magnetic imaging at synchrotron facilities, and theoretical modeling to explore how system size, interaction strength, and structural frustration influence irreversibility and energy dissipation. The results will provide new experimental foundations for nonequilibrium statistical physics and help bridge the gap between theory and realistic nanoscale systems. The project includes strong training and outreach components, engaging students and the public in contemporary nanoscale science. Technical abstract The second law of thermodynamics is strictly valid only in the thermodynamic limit; in small systems driven out of equilibrium, transient violations are predicted by fluctuation theorems. Experimental verification of these predictions in many-body, interacting systems remains limited due to the inability to directly measure microscopic dynamics. This project addresses this gap by employing thermally active artificial spin ice—lithographically defined arrays of dipolar-coupled nanomagnets—as experimentally accessible model systems for nonequilibrium statistical mechanics. Using real-space imaging at synchrotron facilities, the project will directly quantify thermally driven magnetic moment fluctuations under controlled nonequilibrium perturbations. The fluctuation theorem will be tested by constructing the time-integrated dissipation function from experimentally measured microstates and comparing forward and reverse trajectory probabilities. This work will provide the real-space experimental validation of fluctuation theorems in extended, interacting nanoscale systems and advance the application of nonequilibrium thermodynamics to complex physical and technological systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.