Broken Time-Reversal Symmetry Discovered in the Type-I Superconductor YbSb2
The research group of Prof. Ravi Prakash Singh (Department of Physics) has found evidence of unconventional superconductivity in YbSb2, a type-I superconductor. This is unusual, because unconventional pairing of electrons has so far been seen almost exclusively in type-II materials. YbSb2 therefore offers a rare, magnetically simpler platform for studying exotic superconducting states. The team grew single crystals of YbSb2 and confirmed type-I behaviour through electrical resistivity, magnetization, and heat capacity measurements. Muon spin spectroscopy then revealed spontaneous internal magnetic fields appearing below the superconducting transition temperature. This is direct evidence of broken time-reversal symmetry, a hallmark of unconventional superconductivity. First-principles calculations further showed a topological electronic structure and support interband spin-triplet pairing, in which the paired electrons have parallel spins. Together, these features suggest that YbSb2 could host gapless Majorana surface modes, a key ingredient for fault-tolerant quantum computing.For more details, kindly visit https://doi.org/10.1103/drzq-lfn5
