6533b824fe1ef96bd1280c4a

RESEARCH PRODUCT

Superconductivity mediated by spin fluctuations in the heavy-fermion compound UPd2 Al3

subject

description

It is well known that any weak attractive electron–electron interaction in metals can in principle cause the formation of Cooper pairs, which then condense into a superconducting ground state1. In conventional superconductors, this attractive interaction is mediated by lattice vibrations (phonons). But for the heavy-fermion and high-temperature superconductors, alternative pairing interactions are considered to be possible2. For example, the low-temperature properties of heavy-fermion systems are dominated by antiferromagnetic spin fluctuations, which have been considered theoretically3 as a possible cause for Cooper-pair formation. This picture recently received some experimental support: the resistivity behaviour under pressure of two cerium-based heavy-fermion compounds was shown to be consistent with a magnetically mediated pairing mechanism4. Here we use tunnelling spectroscopy to investigate the superconducting order parameter of a uranium-based heavy-fermion superconductor—epitaxial thin films of UPd2 Al3. Our observation of a strong-coupling feature in the tunnelling conductivity, combined with recent inelastic neutron scattering data13,14,15 strongly suggest a pairing interaction mediated by spin fluctuations.