Abstract
We determine the thermal conductance of thin niobium (Nb) wires on a silica substrate in the temperature range of 0.1–0.6 K using electron thermometry based on normal metal-insulator-superconductor tunnel junctions. We find that at 0.6 K, the thermal conductance of Nb is two orders of magnitude lower than that of Al in the superconducting state, and two orders of magnitude below the Wiedemann-Franz conductance calculated with the normal state resistance of the wire. The measured thermal conductance exceeds the prediction of the Bardeen-Cooper-Schrieffer theory, and demonstrates a power law dependence on temperature as T4.5, instead of an exponential one. At the same time, we monitor the temperature profile of the substrate along the Nb wire to observe possible overheating of the phonon bath. We show that Nb can be successfully used for thermal insulation in a nanoscale circuit while simultaneously providing an electrical connection.
Highlights
We determine the thermal conductance of thin niobium (Nb) wires on a silica substrate in the temperature range of 0.1–0.6 K using electron thermometry based on normal metal-insulatorsuperconductor tunnel junctions
We examine experimentally thermal conductance of Nb thin films (200 nm thick, 1 μm wide and 5, 10 and 20 μm long) in the superconducting state (S state) in the temperature range of 0.1–0.6 K
We find that measured thermal conductance of Nb is 2–3 orders of magnitude lower than what is predicted in normal state (N state) in this temperature range
Summary
We determine the thermal conductance of thin niobium (Nb) wires on a silica substrate in the temperature range of 0.1–0.6 K using electron thermometry based on normal metal-insulatorsuperconductor tunnel junctions. Development of new technologies requires sustainable energy supplies[1] To this purpose, the field of thermoelectrics focuses on new materials and devices, such as heat engines[2,3,4] and refrigerators[5,6] for energy harvesting in low-dimensional systems[1,7]. The field of thermoelectrics focuses on new materials and devices, such as heat engines[2,3,4] and refrigerators[5,6] for energy harvesting in low-dimensional systems[1,7] When it comes to mesoscopic devices fabricated at the nanoscale level, control of heat transport is essential[8] and challenging at the same time[9]. It is approximately 2 orders of magnitude smaller than that in Al in S state www.nature.com/scientificreports/
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