The superconducting state occurs when electrons in metals pair up, moving through the conductive material without encountering resistance. The reality is more complex, as German scientists have discovered that electrons can also group into clusters of four, forming a new state of matter and simultaneously opening up potential for new superconducting mechanisms.
The electrical conductivity of a material describes the freedom of electrons within it, but even highly conductive materials like gold still exhibit resistance. The superconducting state offers the possibility of resistance-free electrical conduction; however, it is only stable under extremely low temperatures.
Illustration of four electrons clustering into a group in a superconducting material, as depicted by artist Jörg Bandmann at Pixelwg.
To move easily in a superconducting environment, electrons pair up, transitioning into a Cooper pair state (named after physicist Leon Cooper). This state increases the energy level required to influence the flight trajectory of electrons, and if the average temperature of the material is low enough, atoms will not possess sufficient thermal energy to manipulate the electron pairs. These tiny charged particles will drift freely without losing energy.
In a recent study, scientists from the University of Dresden and Würzburg (Germany) discovered a new connection state of Cooper pairs. In a specific type of superconducting device, electron pairs group together into clusters of four charged particles.
The head of the research team, Henning Klauss, and his colleagues “used multiple methods to confirm the research results,” asserting that “clusters of four electrons appear in certain metals, forming a new state of matter at extremely low temperatures.”
The new superconducting state is only stable at extremely low temperatures.
This phenomenon appears in compounds containing barium, potassium, iron, and arsenic. A decade ago, scientists had certain hypotheses, but evidence was lacking until now. The researchers needed two years of study to reach a final conclusion.
The cluster of four electrons opens up the possibility of a new superconducting state, paving the way for advanced new devices. However, before practical applications can be realized, scientists will need to further investigate how this new state operates, the optimal materials to maintain superconductivity, and how to create clusters of four electrons.
“We can hypothesize that the results will lead to a new line of research, searching for metals that contain clusters of four electrons, or finding ways to modify metals to easily support the four-electron state. Theoretically, a new superconducting state could form due to electron clusters,” concluded researcher Klauss.
