Scientists identify mechanism that explains the characteristic properties of 'strange metals'

'Strange metals' are substances that defy explanation by acting outside of conventional electrical laws, and they have baffled quantum physicists for almost 40 years.

The Center for Computational Quantum Physics (CCQ) at the Flatiron Institute in New York City, under the direction of Aavishkar Patel, has now discovered a mechanism that finally explains the peculiar behaviors of unusual metals.

An answer to one of the most difficult unresolved condensed matter physics issues is provided by Patel and his colleagues in the Science article published on August 18.

Many quantum materials, including some that, with minor modifications, can become superconductors (materials in which electrons flow with zero resistance at low enough temperatures), exhibit strange metal behavior. This connection shows that discovering novel forms of superconductivity may be made possible by comprehending unusual elements.

The surprisingly straightforward new theory explains a variety of peculiarities associated with unusual metals, including why changes in electrical resistivity, which measures how easily electrons can flow through a material as electrical current, are closely correlated with temperature, even at very low temperatures. According to this connection, an unusual metal at a given temperature will impede the passage of electrons more than a common metal like gold or copper.

The new notion is based on a marriage of two peculiar metal characteristics. First, even when separated by great distances, their electrons can become quantum mechanically entangled with one another, tying their destiny. Second, the atom arrangement of unusual metals is irregular and patchwork-like.

Neither characteristic alone can account for the peculiarities of weird metals, but when both characteristics are combined, "everything just falls into place," according to Patel, a Flatiron Research Fellow at the CCQ.

The electron entanglements differ depending on where in the substance the entanglement took occurred due to the odd metal's uneven atomic structure. The electrons' momentum as they pass through the substance and interact with one another is made more random by this variation. Electrical resistance is created when electrons knock one other about in different directions rather of flowing in unison. The electrical resistance increases as a function of temperature because electron collisions increase as a function of material temperature.

"This interplay of entanglement and nonuniformity is a new effect; it hadn't been considered ever before for any material," claims Patel. "Looking back, it was really rather easy. People had been unnecessarily complicating the entire tale of the odd metals for a very long time, and that was wrong.

According to Patel, a deeper comprehension of odd metals might aid in the development and optimization of novel superconductors for uses such as quantum computers.

He explains that there are times when a material tries to become superconducting but is prevented from doing so by a competing condition. The question that arises is whether the existence of these nonuniformities may eliminate the rival states to superconductivity and open the way for it.

The term might no longer seem appropriate given how weird metals have become. At this point, I would prefer to refer to them as uncommon metals rather than odd, adds Patel.

Harvard University's Haoyu Guo, Ilya Esterlis, and Subir Sachdev collaborated with Patel to write the new paper.