A new study shows that nickel oxide superconductors have a type of quantum matter called charge density waves that can accompany superconductivity.
The presence of CDWs shows that nickelates are capable of forming correlated states that can host a variety of quantum phases.
CDWs appear even before we dope the material by replacing some atoms with others to change the number of electrons that are free to move around.
A new playground for studying unconventional superconductors has been created by this new system.
Cuprates and nickelates.
In the 35 years since the first unconventional "high-temperature" superconductors were discovered, researchers have been racing to find one that could carry electricity with no loss. It would be a revolutionary development, allowing things like perfectly efficient power lines, maglev trains and a host of other futuristic, energy saving technologies.
While a vigorous global research effort has pinned down many aspects of their nature and behavior, people still don't know how these materials become superconductivity.
Three years ago, the discovery of nickelate's superconductivity was exciting because it gave scientists a new perspective on the problem.
The nickelates' electronic structure has been explored by researchers. The first high-temperature superconductors, nickelates and copper oxides, were discovered and still hold the world record for high-temperature operation.
Scientists were not surprised to see a kinship between nickel and copper since nickel and copper are on the periodic table. It was not easy to make materials with the right characteristics.
Lee said that this is still very new. People are still trying to understand how different conditions can affect the underlying mechanisms of superconductivity.
The electron waves are frozen.
One of the weird states of matter is CDWs. They are a pattern of frozen electron ripples superimposed on the material's atomic structure with a higher density of electrons in the peaks of the ripples and a lower density of electrons in the troughs.
Various states come and go as researchers adjust the material's temperature. Superconductivity and CDWs can emerge when the material's electrons lose their identities and form an electron soup.
The group did not find CDWs in nickelates with rare-earth elements. The SIMES team created and examined a different nickelate material where lanthanum was replaced with neodymium.
The emergence of CDWs can be very sensitive to strain or disorder in their surroundings, which can be adjusted by using different rare-earth elements.
There are three X-ray light sources that the team carried out experiments at. Tools for probing and understanding the material were offered by each facility. The experiments had to be carried out remote.
It's referred to as'self-doping'.
Even before the material was doped, the nickelate could host both CDWs and superconducting states of matter. It was surprising that this was part of the process of superconducting.
The fact that this nickelate is self-doping makes it different from the cups.
He said that nickelates was an interesting new system for studying how the quantum phases compete. A lot of the tools used to study other unconventional superconductors could be relevant to this one.
More information: Wei-Sheng Lee, A broken translational symmetry state in an infinite-layer nickelate, Nature Physics (2022). DOI: 10.1038/s41567-022-01660-6. www.nature.com/articles/s41567-022-01660-6 Journal information: Nature Physics
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