Superconductivity on the border of itinerant-electron ferromagnetism in UGe2
The absence of simple examples of superconductivity adjoining itinerant-electron ferromagnetism in the phase diagram has for many years cast doubt on the validity of conventional models of magnetically mediated superconductivity. On closer examination, however, very few systems have been studied in the extreme conditions of purity, proximity to the ferromagnetic state and very low temperatures required to test the theory definitively. Here we report the observation of superconductivity on the border of ferromagnetism in a pure system, UGe2, which is known to be qualitatively similar to the classic d-electron ferromagnets. The superconductivity that we observe below 1 K, in a limited pressure range on the border of ferromagnetism, seems to arise from the same electrons that produce band magnetism. In this case, superconductivity is most naturally understood in terms of magnetic as opposed to lattice interactions, and by a spin-triplet rather than the spin-singlet pairing normally associated with nearly antiferromagnetic metals.
Saxena
SS
Department of Physics, University of Cambridge, UK.
Agarwal
P
Ahilan
K
Grosche
FM
Haselwimmer
RK
Steiner
MJ
Pugh
E
Walker
IR
Julian
SR
Monthoux
P
Lonzarich
GG
Huxley
A
Sheikin
I
Braithwaite
D
Flouquet
J