Baeva, E. M., Titova, N. A., Veyrat, L., Sacépé, B., Semenov, A. V., Goltsman, G. N., et al. (2021). Thermal relaxation in metal films bottlenecked by diffuson lattice excitations of amorphous substrates. arXiv:2101.07071v1 [cond-mat.mtrl-sci].
Abstract: Here we examine the role of the amorphous insulating substrate in the thermal relaxation in thin NbN, InOx, and Au/Ni films at temperatures above 5 K. The studied samples are made up of metal bridges on an amorphous insulating layer lying on or suspended above a crystalline substrate. Noise thermometry was used to measure the electron temperature Te of the films as a function of Joule power per unit of area P2D. In all samples, we observe the dependence P2D∝Tne with the exponent n≃2, which is inconsistent with both electron-phonon coupling and Kapitza thermal resistance. In suspended samples, the functional dependence of P2D(Te) on the length of the amorphous insulating layer is consistent with the linear T-dependence of the thermal conductivity, which is related to lattice excitations (diffusons) for the phonon mean free path smaller than the dominant phonon wavelength. Our findings are important for understanding the operation of devices embedded in amorphous dielectrics.
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Li, T. F., Pashkin, Y. A., Astafiev, O., Nakamura, Y., Tsai, J. S., & Im, H. (2008). High-frequency metallic nanomechanical resonators. Appl. Phys. Lett., 92, 043112(1)-043112(3).
Abstract: We developed a technology to fabricate fully metallic doubly clamped beams working as nanomechanical resonators. Measured with a magnetomotive detection scheme, the beams, made of polycrystalline metal films, show as good quality as previously reported ones made of single crystal materials, such as Si, GaAs, AlN, and SiC. Our method is compatible with the conventional fabrication process for nanoscale electronic circuits and thus offers a possibility of easily integrating the beams into superconducting charge and flux qubits and single-electron transistors as well as coupling them to coplanar waveguide resonators.
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Ptitsina, N. G., Chulkova, G. M., Il’in, K. S., Sergeev, A. V., Pochinkov, F. S., Gershenzon, E. M., et al. (1997). Electron-phonon interaction in disordered metal films: The resistivity and electron dephasing rate. Phys. Rev. B, 56(16), 10089–10096.
Abstract: The temperature dependence of the resistance of films of Al, Be, and NbC with small values of the electron mean free path l=1.5–10nm has been measured at 4.2–300 K. The resistance of all the films contains a T2 contribution that is proportional to the residual resistance; this contribution has been attributed to the interference between the elastic electron scattering and the electron-phonon scattering. Fitting the data to the theory of the electron-phonon-impurity interference (M. Yu. Reiser and A. V. Sergeev, Zh. Eksp. Teor. Fiz. 92, 224 (1987) [Sov. Phys. JETP 65, 1291 (1987)]), we obtain constants of interaction of the electrons with transverse phonons, and estimate the contribution of this interaction to the electron dephasing rate in thin films of Au, Al, Be, Nb, and NbC. Our estimates are in a good agreement with the experimental data on the inelastic electron-phonon scattering in these films. This indicates that the interaction of electrons with transverse phonons controls the electron-phonon relaxation rate in thin-metal films over a broad temperature range.
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Santhanam, P., Wind, S., & Prober, D. E. (1987). Localization, superconducting fluctuations, and superconductivity in thin films and narrow wires of aluminum. Phys. Rev. B, 35(7), 3188–3206.
Abstract: We report a comprehensive set of experiments on wide and narrow thin-film strips of aluminum which test the predictions of recent localization theory. The experiments on wide films in the two-dimensional regime confirm the theoretical predictions and also yield insight into inelastic mechanisms and spin-orbit scattering rates. Our extension of the existing theory for one-dimensional systems to include spin-orbit scattering and Maki-Thompson superconducting fluctuations is verified by the experiments. We find clear evidence for one-dimensional localization, with inferred inelastic rates identical to those in two-dimensional films. The prediction of the localization theory for a dimensional crossover from two-dimensional to one-dimensional behavior is also confirmed. We have reanalyzed the results of some previous experiments on thin films and narrow wires in light of these results.
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