A fresh look at metals reveals a 'strange' similarity

We don't have a good understanding of how metals conduct electricity. There are too many exceptions in the current Taxonomy to be convincing. Materials scientists from the University of Groningen looked at the literature on metals and came to this conclusion. A simple formula can be used to give a classification of metals in a more systematic way. On August 29th, their analysis was published.

Electricity is conducted in different ways by metals. Some metals have names such as "correlated," "normal," or "strange." The way in which metals respond to rising temperatures is different in these classes. Professor Beatriz Noheda of the University of Groningen was interested in metals that could change from one state to another. She is the scientific director at the CogniGron research center. We want to make materials that can be both conductors and insulators, but that can also change between those states.

Something that wasn't expected.

She and her colleagues found that the separation between different classes of metals was not clear cut. We decided to take a look at the sample. A group of people, including a former researcher in Noheda's team, used the change in resistivity as a tool to compare more.

There are different scattering mechanisms at different temperatures according to the theory. The result of electron-electron scattering is said to be the cause of a quadratic increase. There is a strict linear behavior that is not yet understood. A linear increase was thought to result from electron-phonon scattering at higher temperatures. saturation should happen at a certain temperature because scattering cannot increase indefinitely. Noheda says that some metals have no saturation within the temperature range.

Noheda and her colleagues were surprised to find that they could fit all the data sets with the same formula. This was a Taylor expansion, in which the resistivity r is described as r 0 + A 1 T + A 2 T 2 + A 3 T 3, in which T is the temperature, while r 0 and the various A values are different constants. A good fit for all the metals can be achieved using just a linear and a quadratic term.

There is more transparency.

The paper shows that the behavior of different types of metals is determined by the relative importance of A 1 and A 2. Noheda says that their formula is a purely mathematical description, without any physics assumptions. The linear and quadratic regimes do not describe different mechanisms such as electron-phonon and electron-electron scattering.

One formula can be used to describe the resistivity of all metals. All metals can now be classified in a way that is more transparent than before. The linear dissipation term at low temperatures can be seen in all metals, thanks to this description. The formula shows that this is the case, even though others had already mentioned it.

Noheda isn't a metal specialist. We had a fresh look at the data after coming from outside the field. We think that people looked for meaning and links to the terms. Maybe some of the conclusions need to be changed. The theory in this field isn't complete. Noheda and her colleagues hope that theoretical physicists will find a way to re-interpretation some of the previous results. Our description allows us to compare metals from different classes.

More information: Qikai Guo et al, Phenomenological classification of metals based on resistivity, Physical Review B (2022). DOI: 10.1103/PhysRevB.106.085141 Journal information: Physical Review B Citation: A fresh look at metals reveals a 'strange' similarity (2022, September 7) retrieved 7 September 2022 from https://phys.org/news/2022-09-fresh-metals-reveals-strange-similarity.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.