Abstract
Sufficiently large electric current applied to metallic nanostructures can bring them far out of equilibrium, resulting in non-Ohmic behaviors characterized by current-dependent resistance. We experimentally demonstrate a linear dependence of resistance on current in microscopic thin-film metallic wires at cryogenic temperatures, and show that our results are inconsistent with common non-Ohmic mechanisms such as Joule heating. As the temperature is increased, the linear dependence becomes smoothed out, resulting in the crossover to behaviors consistent with Joule heating. A plausible explanation for the observed behaviors is the strongly nonequilibrium distribution of phonons generated by the current. Analysis based on this interpretation suggests that the observed anomalous current-dependent resistance can provide information about phonon transport and electron-phonon interaction at nanoscale. The ability to control the properties of phonons generated by current can lead to new routes for the optimization of thermal properties of electronic nanodevices.
- Received 28 June 2019
- Revised 8 December 2019
- Accepted 5 February 2020
DOI:https://doi.org/10.1103/PhysRevX.10.011064
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Joule heating, in which a material’s temperature is increased via electrical currents, is ubiquitous in science and technology. We experimentally demonstrate that, in contrast to macroscopic systems, the effects of electrical current in typical microstructures such as thin-film microwires cannot be described as Joule heating. Phonons generated by the current form a strongly nonequilibrium distribution that cannot be described in terms of temperature, while the quasiballistic flow of phonons from the system cannot be described in terms of heat diffusion. The observed effects are particularly significant at cryogenic temperatures but remain apparent even at temperatures as high as 200 K.
Our findings are relevant to many areas of science and technology. For instance, the effects of current in experiments such as ours provide direct information about electron-phonon interactions, phonon transport, and relaxation at the nanoscale. This can facilitate the design of new materials and structures that more efficiently dissipate heat as well as provide a better understanding of phenomena associated with the electron-phonon interaction, such as superconductivity.
Our results also warrant a reexamination of many experimental observations related to current-induced heating, whose analysis commonly relied on the Joule heating approximation. Furthermore, Joule heating is commonly used in nanoscale heat sources, for example, in studies of thermoelectric phenomena. Our work shows that these effects must be reexamined, which will likely lead to a better understanding of thermoelectric phenomena at nanoscale.