Abstract
We report recent progress of positive muon spin relaxation (μSR) studies on high- T c oxide, organic, heavy-fermion, and Chevrel phase superconductors. μSR measurements of the magnetic field penetration depth λ in more than 30 different hole-doped cuprate compounds have demonstrated strong correlations between T c and 1/λ 2∝ n s/ m∗ (carrier density / effective mass). These correlations can be extended to the organic (BEDT-TTF) 2Cu(NCS) 2 and possibly to Chevrel phase systems. In particular, we found that there are only ∼5–10 superconding pairs in a coherence area ξ 2 on the two-dimensional conducting planes in both the cuprate and organic systems. The penetration depths in UBe 13 and UPt 3 are found to be so long that the μSR measurements can only provide a lower limit on λ ⩾ 10 000 Å. The muon Knight shift is essentially independent of temperature below T c in these heavy fermion systems, indicating a constant spin susceptibility and odd-parity (most likely p-wave) pairing.
Published Version
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