Phase-coherent engineering of electronic heat currents with a Josephson modulator.

In this contribution we report the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of electronic thermal currents.\footnote{A. Fornieri \textit{et al.}, arXiv:1507.00199, to be published in \textit{Nature Nanotechnology}.} The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference\footnote{F. Giazotto and M.-J. Mart\'inez-P\'erez, \textit{Nature} \textbf{492}, 401-405 (2012).} is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid state cooling, thermal isolation, radiation detection, quantum information and thermal logic. Our device provides magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a maximum of the flux-to-temperature transfer coefficient reaching 200 mK per flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the exact correspondence in the phase-engineering of charge and heat currents, breaking ground for advanced caloritronic nanodevices such as thermal splitters, heat pumps and time-dependent electronic engines.