Ok. its a bit brave to nominate myself as an expert, but I work in this field and spent many years studying this compound (this material was the subject of my PhD thesis).
I am a slashdot noob though...
Firstly, I am a bit surprised that this kind of article got slashdotted. The new PRL 'Viewpoint' section which covered this may have helped.
Secondly the evidence for the new state doesn't seem that convincing to me yet. A non-uniform, imperfect flux line lattice (as they observe) is the norm in most materials due to pinning of vortices at impurity sites. The comparison material in their paper (NbSe2) is often studied because of its unusually well behaved lattice, which looks like the textbooks. I would like to see the numbers that they calculate for the apparent 'lumpiness' of the vortex lattice in a range of other superconductors before I drew any conclusion.
Finally, the estimates that they claim put them in the regime of 'type 1.5' are only valid in the clean limit. Impurity scattering, which enhances the penetration depth somewhat, changes these figures. I would say that the experimentally determined penetration depth is larger by a factor of two or three (although these are subject to some uncertainty) which makes the picture quite different, pushing you further towards type II.
Anyway, thats my comment.
PP
Slashdot Mirror
Ok. its a bit brave to nominate myself as an expert, but I work in this field and spent many years studying this compound (this material was the subject of my PhD thesis). I am a slashdot noob though... Firstly, I am a bit surprised that this kind of article got slashdotted. The new PRL 'Viewpoint' section which covered this may have helped. Secondly the evidence for the new state doesn't seem that convincing to me yet. A non-uniform, imperfect flux line lattice (as they observe) is the norm in most materials due to pinning of vortices at impurity sites. The comparison material in their paper (NbSe2) is often studied because of its unusually well behaved lattice, which looks like the textbooks. I would like to see the numbers that they calculate for the apparent 'lumpiness' of the vortex lattice in a range of other superconductors before I drew any conclusion. Finally, the estimates that they claim put them in the regime of 'type 1.5' are only valid in the clean limit. Impurity scattering, which enhances the penetration depth somewhat, changes these figures. I would say that the experimentally determined penetration depth is larger by a factor of two or three (although these are subject to some uncertainty) which makes the picture quite different, pushing you further towards type II. Anyway, thats my comment. PP