232
views
0
recommends
+1 Recommend
0
shares
• Review: found
Is Open Access

Review of 'Evidence for Superconductivity above 260 K in Lanthanum Superhydride at Megabar Pressures'

Bookmark
4
Evidence for Superconductivity above 260 K in Lanthanum Superhydride at Megabar PressuresCrossref
I think the critical temperature (260-270 K) is overrated
 Average rating:     Rated 4 of 5. Level of importance:     Rated 5 of 5. Level of validity:     Rated 3 of 5. Level of completeness:     Rated 3 of 5. Level of comprehensibility:     Rated 4 of 5. Competing interests: None

Reviewed article

• Record: found

(2019)
Bookmark

Review text

I would like to note the problems with Figs. 3 and 4 (PRL). In Fig. 3, the difference between the cooling and warming cycles reaches 12-15 K, which is a lot. This was also initially noted by J. Hirsch when analyzing publications on hydrides. This indicates that the cooling rate was very high, and the cooling process itself and the temperature distribution were most likely inhomogeneous. As subsequent studies have shown, such a large difference in the cooling and heating curves is best avoided. Then there will be no questions and a long discussion about what is the TC of LaH10: 250 K or 260-270 K?

The second remark refers to Fig. 4. It shows that changing the current from 0.1 mA to 10 mA reduces the TC from 280 K to 257 K. In other words, at 257 K we have a critical current of 10 mA. In such a case, using the standard interpolation formula IC= IC(0)*(1-T/TC)s, one finds that s= 4. Then the critical current IC= 2 mA shown in the inset of Fig. 4 for 180 K is clearly not the correct value . At this temperature (180 K), the critical current must be 1000 times greater! And certainly more than 10 mA - the critical current at 257 K. Thus, again questions arise about the correctness of the data presented to support TC > 250 K in LaH10.