Monday, March 31, 2008

Yet more superconductivity fun.

Even more excitement on the novel FeAs-based superconductors. By my count there are seven more papers (0, 1, 2, 3, 4, 5, 6) on tonight's arxiv update, including two different groups demonstrating transition temperatures exceeding 50 K in the Nd version of the compound, and one showing 52 K in the Pr version. Gee, this makes my comments here look prescient. For my next trick, again guided by the periodic table, I suggest that we'll see more rare earth variations. For example, there's no reason not to try the comparatively stable actinides (thorium, protactinium, uranium), or the mostly-filled-f-shell lanthanides (thulium, ytterbium, lutetium) as opposed to the mostly-empty-f-shell ones (La, Ce, Pr). Given that pressure boosts Tc (see paper 1 above), one could try duplicating the effect of pressure by creating more internal stress within the lattice via substitutions of larger atoms between the FeAs layers. Of course, it's easy for me to say this stuff, since I don't actually have to make the compounds....

It's also worth noting that early photoemission data and heat capacity measurements on a couple of the compounds strongly suggest that the superconducting gap is zero (or darned close to it) on at least part of the Fermi surface. This is the case for the cuprates, and exactly not the case in conventional low temperature superconductors.

4 comments:

Anonymous said...

I think you missed

http://arxiv.org/abs/0803.4234

Doug Natelson said...

Fixed - thanks.

CarlBrannen said...

The cool thing about these superconductors is that they are such simple crystals. It makes me suspect that it will be possible to build them up from vapor deposition and that smells like integrated circuit manufacturing techniques. Of course that means a lot more techniques for getting physics out of them.

So what tetragonal crystal would make a suitable base for vapor deposition? I've always been fond of rutile and cassiterite.

Senior Facility said...

It makes me suspect that it will be possible to build them up from vapor deposition and that smells like integrated circuit manufacturing techniques.