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Title: Symmetry of the superconducting order parameter of UTe2
Plain: UTe2 is a heavy-fermion superconductor whose electron pairs probably have parallel spins (spin-triplet), but the exact pairing pattern is still argued over.
Precise: Determine the irreducible representation of the superconducting order parameter of orthorhombic UTe2 (point group D2h; candidates B3u, B2u, Au, or multicomponent combinations) at ambient pressure and zero field, including node positions and whether time-reversal symmetry is broken. An answer is a set of measurements (Knight shift along a, b, c; directional thermal conductivity; polar Kerr; quasiparticle interference of surface states) consistent with one representation.
Settled by: Knight shift along all three axes in high-quality crystals plus a phase-sensitive surface probe that singles out one representation.
Kind: well-posed
Answer type: identification
References: (empty)
Literature status: contested
Status note: Odd-parity pairing is supported by several probes; resonant ultrasound (2024) indicates a single-component order parameter, thermal conductivity (2026) reports point-like gap minima that do not reach zero, and polar Kerr evidence for time-reversal breaking was not reproduced in cleaner crystals (2023).
Posed since: 2019