Modification of Electron-Phonon Coupling by Micromachining and Suspension

Weak electron-phonon interaction in metals at low temperatures forms the basis of operation for cryogenic hot-electron detectors. Standard power laws, describing the heat flow in the majority of experiments, have been identified and derived theoretically. However, a full picture encompassing experimentally relevant effects such as reduced dimensionality, material interfaces, and disorder is in its infancy, and has not been tested extensively.

Here [1], we study the electron-phonon heat flow in a thin gold film on a suspended SiO₂ platform at temperatures below 100 mK using supercurrent thermometry. We observe a half-integer power law that has been recently predicted by theory [2], defying conventional results for bulk (semi-infinite) systems. The novel thermometry method we employ addresses some of the shortcomings of conventional nanoscale thermal measurement schemes. Similar behavior has been reported in earlier work [3].

[1] O.-P. Saira et al., arXiv:1910.10126 (2019).
[2] D.-V. Anghel et al., Phys. Scr. 94 105704 (2019).
[3] J. T. Karvonen and I. J. Maasilta, Phys. Rev. Lett. 99 145503 (2007).