Raffi Budakian

Direct measurement of dipolar spin transport on atomic length scales

Raffi Budakian - University of Waterloo, Canada

Understanding the quantum dynamics of interacting spins is central to a wide range of phenomena, including magnetism, superconductivity, and quantum spin liquids. One of the most direct ways to study these dynamics is by observing how many-body quantum states evolve under spin interactions. While the idea is simple in principle, realizing such experiments in practice remains challenging. Some of the earliest progress came from NMR, where multiple quantum coherence techniques provided powerful tools for tracking the growth of correlations in interacting spin systems. More recently, advances in quantum platforms—such as ultracold atoms, Rydberg arrays, and solid-state quantum sensors—have dramatically expanded our ability to control and interrogate many-body quantum dynamics. In this talk, I’ll share recent results from a force-detected nanoscale NMR platform that enables direct measurement of Zeeman order transport driven by dipole-dipole interactions among 31P spins in single-crystal InP. Leveraging large magnetic field gradients and long spin coherence times, our platform allows us to resolve transport on length scales ranging from 3 Å—smaller than the average 31P–31P spacing—up to 10 nm. By selectively coupling to the disordered magnetic environment of the indium nuclear spins, we can further investigate how strong disorder influences spin transport. I’ll also compare our experimental findings with a semi-classical mean field theory of spin diffusion, and discuss the limits of its applicability in describing transport at the nanoscale.