Observation of second sound in a rapidly varying temperature field in Ge

A Beardo and M Lopez-Suarez and LA Perez and L Sendra and MI Alonso and C Melis and J Bafaluy and J Camacho and L Colombo and R Rurali and FX Alvarez and JS Reparaz, SCIENCE ADVANCES, 7, eabg4677 (2021).

DOI: 10.1126/sciadv.abg4677

Second sound is known as the thermal transport regime where heat is carried by temperature waves. Its experimental observation was previously restricted to a small number of materials, usually in rather narrow temperature windows. We show that it is possible to overcome these limitations by driving the system with a rapidly varying temperature field. High-frequency second sound is demonstrated in bulk natural Ge between 7 K and room temperature by studying the phase lag of the thermal response under a harmonic high-frequency external thermal excitation and addressing the relaxation time and the propagation velocity of the heat waves. These results provide a route to investigate the potential of wave-like heat transport in almost any material, opening opportunities to control heat through its oscillatory nature.

Return to Publications page