tag:blogger.com,1999:blog-13869903.post6408284344429364948..comments2024-03-28T04:15:44.459-05:00Comments on nanoscale views: This week in cond-matDouglas Natelsonhttp://www.blogger.com/profile/13340091255404229559noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-13869903.post-68569821710106694882007-06-12T07:30:00.000-05:002007-06-12T07:30:00.000-05:00I agree that the experiments proving order vs. dis...I agree that the experiments proving order vs. disorder effects will be challenging. But it seems to me that a whole lot of weight is currently hanging on this issue - is this simple premelting at grain boundaries/dislocations/other deffects, or is there a true supersolidity component?<BR/><BR/>I also wonder how much collaborative effort can contribute to resolving these controversies - for example, can someone from Chan group travel to Reppy's group in Cornell, or even go to France or Canada to see what they are doing and tell them first-hand how they grow their crystals? This would obviously work only if everyone truly wants to resolve this puzzle/controversy as quickly as possible. From purely selfish motives it may be more beneficial for everyone to keep exchanging high profile papers with "it's supersolid" "nope, it's not!" "it is so!". Not saying this is what's happening here, but often it seems to be the case that even a sniff of controversy provides more visibility to the issue than some boring measurement that everyone agrees on.NONEhttps://www.blogger.com/profile/10714684038171784902noreply@blogger.comtag:blogger.com,1999:blog-13869903.post-41053589914403918822007-06-11T08:58:00.000-05:002007-06-11T08:58:00.000-05:00IP - Yeah, the 4He guys have it rough. With 3He c...IP - Yeah, the 4He guys have it rough. With 3He crystals, you can do NMR with field gradients (basically MRI) and figure out if you really have a single crystal. Since 4He has no nuclear moment, that's not an option here. Crystallography is tough, too, of course, since the crystals have to be grown at high pressures inside metal containers - x-rays are basically out; neutrons are a possibility, but cross-sections for 4He are low. Hmmm. Ultrasound? I remember at some point that at least one group was looking at 4He crystals with an optical camera, but I can't find the reference anywhere. Definitely a hard experimental problem. Even if one could see large crystal boundaries, I'm not sure how one could ever rule out disordered layers at the walls.Douglas Natelsonhttps://www.blogger.com/profile/13340091255404229559noreply@blogger.comtag:blogger.com,1999:blog-13869903.post-71925354872075212202007-06-09T14:09:00.000-05:002007-06-09T14:09:00.000-05:00btw - this is one example how arxiv could benefit ...btw - this is one example how arxiv could benefit from "comments" sectionNONEhttps://www.blogger.com/profile/10714684038171784902noreply@blogger.comtag:blogger.com,1999:blog-13869903.post-48285021375280493412007-06-09T14:04:00.000-05:002007-06-09T14:04:00.000-05:00Doug, thanks for highlights.Maybe I am being too c...Doug, thanks for highlights.<BR/>Maybe I am being too critical, but the supersolid paper should be titled: "NCRI in single crystal (likely, perhaps, maybe, at least we think so) helium".<BR/><BR/>Growth of single crystals is more art than science, it's a bit like cooking - and following certain recipe does not in fact guarantee that you end up with the same result.<BR/><BR/>I agree with conclusions of Phillips and Balatsky paper - structural measurements - x-ray tomography or microscopy, or neutron scattering is really crucial to resolving the current controversy. Without some sort of crystallography data arguing that this paper reports "NCRIF in (very likely) single crystal samples" - an actual quote from Clark/Chan paper - is likely to cause only more controversy on this subject.<BR/><BR/>Don't get me wrong - I think Chan and his group are very careful and professional, but in this case they could have pushed the envelope a bit further, perhaps with some help from x-ray/neutron folks, or some other structural characterization. Otherwise, I am (for one) not really convinced.NONEhttps://www.blogger.com/profile/10714684038171784902noreply@blogger.com