Phonon-dominated thermal conductivity of a superconducting amorphous MoSi thin film
We use the differential 3ω method to directly measure the temperature dependent thermal conductivity for about 90 nm Mo0.78Si0.22 thin films. The measurements are performed in a closed-cycle cryostat to access the temperature range between 50 K and 300 K. The MoSi thin films are capped with Al2O3 and probed with a Pt wire. The results show that the thermal conductivity does not satisfy the Wiedemann-Franz law. This implies that thermal transport in MoSi is not dominated by electrons but by phonon-like excitations, contrary to what is assumed in many electro-thermal models of superconducting devices. We argue that this property might be related to the weak localization visible in the resistivity as a function of temperature curves of the superconductor.