The universities of Kent, Bristol along with Huddersfield and Rutherford Appleton Laboratory researchers have found a new unusual series of unconventional superconductors.
Latest research on superconductivity targets Cooper pairs’ internal structure. In conventional as well as in certain high-temperature superconductors, the electrons within a Cooper pair have intrinsic ‘spins’ opposite to each other having zero net spin of the Cooper pair. Triplet superconductors such as strontium ruthernate Sr2RuO4 represent Cooper pair having its own intrinsic spin that is randomly-oriented; the condensate of Cooper pairs has no net spin. The ‘non-unitary’ triplet superconductors have specifically directed spins of the Cooper pairs.
The materials within all known non-unitary triplet superconductors were ferromagnetic. Prior to superconductivity, the spins of their electrons acting as tiny bar magnets were aligned in a specific direction. The superconductor LaNiC2 was shown to be a non-unitary triplet superconductor in 2009.
The present team has demonstrated another material having LaNiGa2 property. Based on the muon spin rotation technique, the measurements were conducted at the ISIS Facility, Rutherford Appleton Laboratory. By bombarding a sheet of graphite with a proton beam using Particle accelerator, muons results which when disintegrated emits a positron that is detected by the experimental apparatus. The emission of the positron shows details about the atomic-scale distribution of magnetization within the material.
In contrast to its cousin LaNiC2, the new superconductor’s crystal structure has symmetry under inversion. These two instances of a new family of superconductors possess non-unitary triplet pairing besides being non-ferromagnetic. Using fundamental symmetries of nature, these materials show ‘paramagnetism’. Magnetisation results in response to the Cooper pairs’ magnetic moments. The challenge is to comprehend the microscopic understanding of creating this highly-exotic pairing structure.
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