3 ms·
This is probably a very stupid question, but why is simply measuring resistance not enough to conclusively prove that it is a superconductor. I mean, isn't zero
by weinzierl 3y ago
This is probably a very stupid question, but why is simply measuring resistance not enough to conclusively prove that it is a superconductor. I mean, isn't zero resistance the defining property?
- vrotaru 3y agoWell, I guess, that are islands of superconductivity and normal conductivity in the same sample. This gives a low resistance and diamagnetism which is used as proxy to real superconductivity. I may be wrong though.
- OJFord 3y agoI think if it was actually zero it would be? The issue I think is impurity/defects in the manufactured samples, so there's non-superconducting bits in addition to the allegedly superconducting bits.
- rvnx 3y agoJust guessing: I would say not enough because the sample is extremely small and there is chance that the electrons jump from each sides of the probes, skipping the sample ? (like a short-circuit) + the fact that the probes themselves are not superconductor, so there is a natural accepted tolerance in the measures (claimed to be due to the probes)
- mianos 3y agoIf the video is to be believed, the samples shown are huge compared to a, trivial to make, pulled or cut platinum wire probe. You could just put it on a plate in an SPM and measure it. So many questions. I assume this is all possible but they are focussing on one thing at a time to duplicate the results, if possible.
- baq 3y agoMeasuring zero resistance turns out to be quite difficult because your measuring apparatus tends to have some resistance in itself. Perhaps heating it up while it levitates would be a better idea. Put the magnet in an oven together with the sample and bake?
- marcosdumay 3y agoMagnets have an annoying tendency to stop working when they are heated. And it's ridiculous that I'm saying that on the context of testing a superconductor. But well, here we are.
- archontes 3y agoYou could always use an electromagnet.
- jacquesm 3y agoA superconducting one?
- archontes 3y agoNo, we're talking about verifying superconductivity using a traditional magnet at an elevated temperature.
- marcosdumay 3y agoYes, but that's quite a bit of extra complication on an experiment of some material that was announced into the world last Friday. I do expect people to fully characterize it eventually.
- jacquesm 3y agoIndeed, that statement would have been really funny just a few weeks ago. Now you're going to have to wonder whether the magnet or the superconductor will fail first. Neo magnet fabrication is fascinating by the way, the somewhat magnetized blanks are not all that impressive from a magnetic field strength point of view, but then you zap them with a strong enough field and they then suddenly are the best thing since sliced bread. This technique was first developed for 'regular' ceramic magnets. https://idealmagnetsolutions.com/knowledge-base/how-neodymium-magnets-made/ https://idealmagnetsolutions.com/knowledge-base/how-neodymiu... An uncoated magnet will oxidize very fast, so you always have to ensure that the coating on any magnets you use is perfect or the magnet will surely fail.
- mensetmanusman 3y agoBecause materials interfaces create weird effects. You would use metals as your leads and create Josephson-junctions-like interfaces. Basically the abrupt change in electron mobility across materials can cause knock on effects that dominate what you are trying to measure. Interfacial engineering is one term in materials science that implements best practices for dealing with such challenges.