Paper abstract
The ability to understand, control, and engineer heat flow is central to applications ranging from energy conversion to thermal management. Heat transport is particularly interesting at the micro- and nanoscale, where the conventional description of diffusive heat conduction can break down and where interfacial thermal transport becomes increasingly relevant. Probing nanoscale heat transport requires experimental methods that are non-invasive, compatible with ultrathin samples, and capable of resolving heat dynamics across interfaces between different materials. Optical pump-probe techniques provide a powerful contactless solution, combining high spatial and temporal resolution to accurately map the temporal dynamics and spatial evolution of material temperatures. Here, we first discuss the recently established technique of spatiotemporal thermometry (STT), which is particularly suitable for in-plane thermal transport. We then propose the technique of material-selective time-resolved thermometry, which is particularly suitable for out-of-plane heat transport. Both techniques follow the evolution of the temperature of thin films in time and space. Together, these two time-resolved approaches provide a platform for quantifying heat transport parameters in materials down to atomic thicknesses, with great potential for exploring nanoscale thermal phenomena.