# Superconductivity and entropy

1. Jul 10, 2013

### anuraj.b

According to theory of superconductivity, resistivity almost zero. Below critical temperature the entropy decreases markedly with cooling .
why resistivity zero when entropy not equal to zero?
my doubt is when there is an entropy there is a disorder. then how can move conducting electron freely and zero resistivity occur ? if you know please replay

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2. Jul 10, 2013

### Staff: Mentor

Exactly, not almost.

Where is the issue? Note that not all particles in the material contribute to superconductivity.

3. Jul 10, 2013

### anuraj.b

you know when resistivity is zero then cooper electrons move freely. but the problem is the entropy not equal to zero , the atoms in the superconductor vibrate its mean position. then how can cooper electron move freely?

4. Jul 11, 2013

### Staff: Mentor

I still don't see the issue.

5. Jul 11, 2013

### ZapperZ

Staff Emeritus
You do know that the "entropy" here is the entropy of the whole material? mfb has indicated that NOT ALL ELECTRONS PARTICIPATE IN SUPERCONDUCTIVITY (sorry, I had to bold it and cap it since you appear to have missed it the first time around). So there are normal-state electrons in the material that are not part of the supercurrent.

Furthermore, superconductivity does NOT occur just at 0 K. In fact, in high-Tc superconductors, the transition temperatures can be as high as 100-130 K! The lattice still has considerable vibrations at those temperatures. So why would entropy be zero when there is a non-zero finite temperature?

You haven't made much attempt to try and connect why "zero resistance" MUST somehow imply "zero entropy". On the other hands, you'll notice that I've had to type quite a bit (more than all of your posts combined so far) in explaining to you why it can't be zero.

Zz.