Colloquia

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The discovery of superconductivity in CeCu₂Si₂ nearly 20 years ago was totally unexpected and contradicted fundamental tenants of the well-established BCS theory of superconductivity. Instead of the magnetic moment carried by Ce+3 suppressing superconductivity, as expected from BCS, the presence of Ce was essential for superconductivity and responsible for increasing the effective mass of the electrons participating in superconductivity by orders-of-magnitude-hence, heavy-fermion superconductivity. As we now know, CeCu₂Si₂ was the first example of superconductivity mediated by antiferromagnetic spin fluctuations, which also may be the dominant pairing mechanism in high-temperature superconductors, and other parallels between heavy-fermion and cuprate superconductivity are emerging. Recently, we have discovered a new family of heavy-fermion materials, CeMInsub₅ (M=Rh, Co, and Ir), in which superconductivity appears at temperatures higher than in any other heavy-fermion system. These materials form in a quasi-2D structure, which makes an analogy with the cuprate's magnetism and superconductivity appealing. Though much remains to be learned about their properties, this new family appears to be quite interesting and provocative.