Strong-coupling d-wave superconductivity in PuCoGa₅ probed by point-contact spectroscopy.
Nat Commun 2012;
3:786. [PMID:
22510691 PMCID:
PMC3337991 DOI:
10.1038/ncomms1785]
[Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Accepted: 03/09/2012] [Indexed: 11/16/2022] Open
Abstract
Superconductivity is due to an attractive interaction between electrons that, below a critical temperature, drives them to form Cooper pairs and to condense into a ground state separated by an energy gap from the unpaired states. In the simplest cases, the pairing is mediated by lattice vibrations and the wavefunction of the pairs is isotropic. Less conventional pairing mechanisms can favour more exotic symmetries of the Cooper pairs. Here, we report on point-contact spectroscopy measurements in PuCoGa5, a moderate heavy-fermion superconductor with a record high critical temperature Tc=18.5 K. The results prove that the wavefunction of the paired electrons has a d-wave symmetry, with four lobes and nodes, and show that the pairing is likely to be mediated by spin fluctuations. Electronic structure calculations, which take into account the full structure of the f-orbital multiplets of Pu, provide a hint of the possible origin of these fluctuations.
The heavy-fermion material PuCoGa5 is characterized by unconventional superconducting properties. By combining point-contact spectroscopy and first-principles calculations, this study reveals a d-wave symmetry in the system's order parameter.
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