Engineering Thermal Transport in Atomic Seale Devices and Nanoscale Gaps

Understanding and controlling heat flow at the nanoscale is a grand challenge with implications for electronics, energy conversion, and emerging quantum technologies. Over the past decade, our group has developed a suite of nanofabricated calorimetric platforms — capable of picowatt-level sensitivity — that have opened experimental access to thermal phenomena previously beyond reach. These tools have allowed us to demonstrate hundred-fold enhancements in far-field radiative heat transfer beyond the blackbody limit, perform the first direct measurements of thermal conductance of single-molecule junctions, and realize nanoscale photonic thermal transistors capable of sub-second heat-flow switching. In this talk, I will describe how we are now leveraging these platforms to achieve new levels of control over thermal transport. Using cryogenic calorimetric scanning probes, we show that replacing a single hydrogen atom in a molecular junction with progressively heavier halogens tunes the thermal conductance by up to a factor of two — without altering electrical conductance — revealing that phonon transport can be engineered with true atomic precision through modification of vibrational eigenmodes and the creation of antiresonances in the phonon transmission function (Y. Luan et al., Nature Materials, 2026). Extending our capabilities to cryogenic temperatures, we demonstrate the first near-field thermal diode, in which the superconducting phase transition of niobium suppresses radiative heat transport across a nanogap by approximately 20-fold and enables thermal rectification of 70%, pointing toward new strategies for thermal management in quantum computing architectures (Y. Luan et al., Nature Nanotechnology, 2026). I will close by previewing two emerging directions in the group: direct measurements of Casimir forces in nanoscale gaps and the search for persistent thermal currents that are analogous to electrical supercurrents in superconductors.