LAUSR

Thermal Transport Between the two extremes of ballistic and diffusive lattice thermal transport is the potential for an exotic wave-like state known as second sound. Huberman et al. used fast, transient thermal grating measurements to show the existence of second sound in graphite between 85 and 125 kelvin (see the Perspective by Shi). Previous observations of second sound have been rare, confined to isotopically pure materials at very low temperatures. The observation of second sound in graphite is likely due to its layered nature, suggesting that this thermal transport mode may be accessible in other two-dimensional materials. Science , this issue p. [375][1]; see also p. [332][2] [1]: /lookup/doi/10.1126/science.aav3548 [2]: /lookup/doi/10.1126/science.aax2319