Extraordinary claims require extraordinary evidence
Carl Sagan - Cosmos
Several people have been in contact with questions about a new physics paper on a room temperature superconductor. It’s a big thing it’s real and if it can be developed into something practical. I skimmed the paper at first and then gave a more careful read. So here are a few early comments.
First the background. Superconductors conduct electricity without resistance, but there are caveats. The most useful ones need to be cooled to liquid helium temperatures. At normal atmosphere pressures that’s about 4.2 K .. really cold! (absolute zero is 0 K). Helium is very expensive, in short supply if you want scale and expensive to liquify and keep in a liquid state. LHe temperature superconductors are used in superconducting magnets that produce very high magnetic fields - physics experiments, maglev vehicles and MRI machines are major users. For the last 25 years or so we’ve had superconductors that work at liquid nitrogen temperatures. LN2 is comparatively inexpensive and fairly easy to handle. The problem is they don’t support high electric currents or magnetic fields.. There’s been a lot of focused research working on this with the best materials known as ReBCO (rare earth barium copper oxides) - there’s a largish family. They do support relatively high current densities and magnetic fields at liquid hydrogen temperatures. LH2 is between LHe and LN2 in temperature. It’s much cheaper than liquid helium. Currently the cost of LH2 temperature superconductors is about four times that of conventional materials in high field magnets. Getting down to the same cost would be a big thing.
There has been work on much higher temperature superconductors - some work suggested it could be done at room temperature, but at very high pressures. That was a couple of years ago, but there are questions with the experimental work and the very high pressure requirement makes it impractical. But if it turns out to be real, it could provide useful insight.
So onto the current paper. It shows superconductivity at and somewhat above room temperature (up to 400 K!) and at sea level pressures.
Reading the paper I see a number of red flags. It hasn't been peer reviewed yet. None of the authors is known in the field and they’re from an institute that doesn’t have a track record. Important discoveries are sometimes made outside of the field, but it’s VERY rare. They talk about critical (magnetic) field and critical current. Both numbers are extremely low - far too low to be practical. Also critical current doesn’t mean anything .. the right metic is critical current density. It’s not a typo .. their graph shows current rather than current density. More troubling is they don’t find a Tc (critical temperature).. they only state it’s still superconducting at 400 K. The fact they can’t make it go away raises red flags.
You also need to demonstrate the Meisner effect - the exclusion of magnetic fields - it gets technical, so I won’t go into details, but just noticing a drop in resistance isn’t enough. They do claim a Meisner effect, but their graph doesn’t show it. It looks like garden variety diamagnetism.
There are a few other technical issues, but I think I've made my point.
They offer a theory of what’s going on, but it’s ad hoc-ish. That’s not really a problem - an experimental result doesn’t need a theory. But why do they try? red flag.
It should be easy to replicate. Their technique strikes me as sloppy. It’s possible they’ve discovered something. We’ll know quickly as this should be straightforward to try and replicate. If it’s real and the magnetic field is what they show, it isn’t practical. It would offer a window into a different class of materials to try.
For now, color me skeptical. Extraordinary claims require extraordinary evidence. They don’t offer much in the way of evidence. I worry we have another Pons and Fleishmann paper. A big sin was P-F publicly claimed they had made a fusion breakthrough with cold fusion and the media jumped onto it. At least these guys don’t seem to be banging the publicity drum.
LH2 class superconductors may be very practical for many commercial applications in the next five to ten years. That’s a very important area that could become commercial soon. It would be even better if it can work at LN2 temperatures, but so far it’s been disappointing.
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