YbSb₂ shows time-reversal symmetry breaking in a type-I superconductor
Researchers led by IISER Bhopal report that YbSb₂, a type-I superconductor, generates tiny internal magnetic fields as it enters its superconducting state—the first such observation in a type-I material. The result, published in Physical Review Letters, points to an unexpected quantum state, but proposed links to Majorana modes and quantum computing remain theoretical.
Bottom line — YbSb₂ superconducts below 0.95 K; confirming its proposed Majorana surface modes will require further experiments.
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The research team used implanted muons to detect an internal field of about 0.44 gauss when the crystals became superconducting, according to Xenospectrum.
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Xenospectrum reports that the team’s measurements also supported type-I behaviour: the crystals expelled magnetic fields until superconductivity ended.
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The researchers propose an internally antisymmetric nonunitary triplet, or INT, state to explain the spontaneous field; the pairing state has not been directly confirmed.
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Calculations suggest the proposed state may support gapless Majorana surface modes. Direct evidence for those modes has not been reported.
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YbSb₂ is not a newly discovered material: Xenospectrum notes that an earlier study described it as a type-I superconductor in 2012.