A team of physicists from the University of Washington and the U.S. Department of Energy (DOE) appears to have discovered a new, controlled type of superconductivity in an exotic crystal-like material. Its superconductivity can be changed until it is completely turned off, depending on the deformation applied to it. At the same time, the record for how “hot” a field-effect superconductor can get before it loses its ability to conduct electricity without encountering any resistance has apparently been broken.

A scientific paper published in the journal Science Advances describes a synthetic crystal-like sandwich of ferromagnetic (europium) and superconducting materials (iron arsenide) that exhibits superconductivity when placed near a sufficiently strong magnetic field. The EuFe2As2 doped crystal, so named because of the addition of cobalt molecules in the synthesis process, takes advantage of the strong ferromagnetism of europium (Eu) alternating with superconducting FeAs layers (iron arsenide) in a sandwich configuration.

The result is a magnetic field-tunable superconductor; superconductivity can be activated using external magnetic fields. In case of doped crystal EuFe2As2 (using a combination of specialized equipment and X-ray techniques) the research team demonstrated how a properly aligned external magnetic field balances magnetic fields arising from ferromagnetic europium layers. This allows them to be reoriented, and a zero-resistance state of matter arises as soon as the initially chaotic magnetic fields become parallel to the superconducting ones.

But the doped EuFe2As2 crystal has another interesting property: its superconducting abilities can be turned off even in a fairly strong magnetic field. All that needs to be done for this is to deform the material with a cryogenic strain gauge and apply pressure from one side (uniaxial) with a special industrial piston approved for scientific measurements. This changes the degree of resistance of the electrons passing through it. At certain deformation levels, the superconductivity of the synthetic material can be increased to the point that an external magnetic field is not needed to transition to the superconducting state. However, after a certain point, even extreme pressure does not allow the process to begin.

Researchers pointed out difficulties in the synthesis process. Therefore, the group could not determine what prevented them from obtaining stable cobalt-doped EuFe2As2 samples as a result of synthesis; instead they reported “significant variability of samples ”, where variability is understood as the presence or absence of field-induced superconductivity. The researchers also noted that the difficulties most likely arise in the cobalt doping step, confirming how difficult it is to control quantum processes (like chemical reactions) with the level of precision required by some of these synthetic superconducting materials.

All it takes to transform a material from semiconductor to superconductor are subtle, subatomic changes and interactions of the elements. But behind this simplicity lies a complex interplay of elements, particles and subatomic particles, spins, magnetic fields and many other parameters that must be exactly as needed or, in the case of the samples in study, at temperatures between 4 and 4°C. 10 Kelvin.

This level of resolution and control over the “off” moment of superconductivity (the same as the “on” moment, but in a special quantum sense) should provide invaluable insights into the quantum physics of superconductivity. At the very least, the rediscovered superconductor could be a test bed for a better understanding of superconductivity. The research leads to the possibility of seeing the molecular transition from ordinary matter to the superconducting phase and should improve our ability to control and exploit this effect. For example, this discovery could find application in superconducting circuits for next-generation industrial electronics.