[wereworm73]

I was wondering....Have scientists ever experimented with different barium isotopes in yttrium barium cuprate?

Looking at the abundance of stable barium isotopes, about 1 out of 6 barium atoms should have a +3/2 spin while the rest have +0 spin.  But what happens to the superconductor's Tc if they only used Ba-137 (which has a +3/2 spin) or Ba-138 (which has +0)?  I sometimes read about quantum mechanics being responsible for the superconducting behavior in YBCO; so, I'm wondering if it would be better if all the barium atoms were fermions or bosons (instead of a mixture). 

[Borek]

Interesting question, but IMHO it is more about electrons then nuclei, so the difference can be below measurement level.

[wereworm73]

Yes, but something about the structure of YBCO is causing the electrons to behave much differently than they would in a normal conductor.

One of the things I noticed about YBCO is that the spin for yttrium, copper and oxygen is very consistent throughout the whole structure.  Yttrium only has one stable isotope and its spin is 1/2-, so all the yttrium in the superconductor can only have a spin of 1/2- (unless you've made a radioactive superconductor).  The naturally-occuring, stable istopes of copper both have a spin of 3/2-, and the vast majority of oxygen atoms (O-16) have a zero spin.  So, you'd basically have 3/2- and 0+ consistently alternating throughout the entire cuprate plane.  I don't know if this whole fermion-boson-fermion-boson pattern can somehow force electrons to move in an orderly fashion through the superconductor, but a lot of other high temperature superconductors are cuprates too.

Barium is the only component in this superconductor that can have different spins due to having several stable isotopes.   So I'm curious about isotope effects for that.

[Bakegaku]

I haven't read anything about use of different Barium isotopes in this superconductor, but I read once that they used different copper isotopes to see if the mass had any effects.  They found that heavier copper isotopes produced a slightly higher T_c