klimt · HackerTrans

3 năm trướcdiscuss

This is one of my key takeaways as well. It's a shame they didn't include their magnetization measurements, even if it didn't confirm superconductivity. The first conclusive paper will have to demonstrate a superconducting transition in both electrical resistivity and magnetization.

klimt

3 năm trướcdiscuss

Extrapolated.

klimt

3 năm trướcdiscuss

YBCO which has a critical temperature of around 90K has a critical field in excess of 250T. So 9T is not expected to weaken superconductivity much for a sample with a critical temperature of 110K.

klimt

3 năm trướcdiscuss

The jump looks like bad contacts to me. The wires you attach undergo stress during the cooldown, and such artefacts can happen with small samples. Rewiring the sample should get rid of it.

klimt

3 năm trướcdiscuss

The jump at 250K looks like bad contacts to me that fixed themselves during cooldown. Rewiring the sample and remeasuring should get rid of it. The field dependence is indeed a bit weird. One would expect the critical temperature to reduce with increasing magnetic field (magnetic field weakens superconductivity), but here you don't see that. It's expected that the superconductivity is very strong for such a high critical temperature and the fields applied are not strong enough, but with better measurements you should still see a small reduction in the critical temperature.

klimt

3 năm trướcdiscuss

This is my first comment on this material, because I've been skeptical, but this result shouldn't be understated. It basically confirms the existence of a new family of high-temperature superconductors, the first of its kind since the cuprates in 1986. And for context, in the initial paper on the cuprates the critical temperature was measured to be 36 K. By synthesising other members of the cuprate family and optimising the growth, it was possible to raise it to 127 K in the subsequent few years. The 110 K seen today for LK-99 sets a baseline, and it's a very good baseline at that. Confirm me as excited.

klimt

5 năm trướcdiscuss

It's Cell Patterns, a new open access journal from Cell Press that started in April 2021.

klimt

6 năm trướcdiscuss

I had to give it 3-4 days before I got some activity. Any flour should work as long as it is unbleached. I've had good success with just Sainsbury's strong white bread flour. It has given me a fragrant peachy starter.

klimt

7 năm trướcdiscuss

> one of the researchers carefully sandwiches lanthanum foil and hydrogen gas in between the diamonds’ flat surfaces. Then [...] the researcher generates pressures of at least 170 GPa—pressures similar to those in the Earth’s core—between the diamond tips. Then [...] the team heat the material with laser pulses, producing the chemical reaction that would create the material.

It is always humbling to read about what it takes to do cutting edge research. This article was good at conveying the efforts required.

I do wonder if studying these simple hydrogen-based compounds is a dead end though. I believe the same mechanism (phonon-electron coupling) is at work here, than in conventional superconductors, so the physics is well-understood. It's been established that this mechanism can only support superconductivity up to 30-40 K at normal pressures [1]. Unconventional superconductors, on the other hand, don't have this hard limit, so there is probably more knowledge to be gained from studying those, which could be used to propose new, better superconductors.

[1] https://en.wikipedia.org/wiki/BCS_theory

klimt

8 năm trướcdiscuss

The only connection to black holes that I could find is, that they use mathematics first developed for string theory [1], so it's bit tenuous to say superconductors are related to black holes. Once you read a few of these articles you start seeing the same tropes. I yearn for articles with less hype, and more honesty.

The main result of the paper seems to be Fig. 3B and Fig. 4B. The black line represents the limit set by the uncertainty principle, and they argue that all these superconductors lie right at the limit, which they call Planckian dissipation. However, I have a sense that a lot of cherry-picking data is going on. They claim this is a universal behaviour, but the paper doesn't even mention whether it applies to the most well-known and highest temperature superconductors like YBCO and HBCCO. I suspect because it doesn't. Another omission is NCCO, for which they have data for in Fig. 4A (from which Fig. 4B is calculated), but then they don't plot it in Fig. 4B. I am guessing because it again didn't match claim. I wonder how thorough the review process was, if at all.

[1] https://en.wikipedia.org/wiki/AdS/CFT_correspondence#Condens...

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