tag:blogger.com,1999:blog-13869903.post115549565348536907..comments2024-03-29T02:45:10.096-05:00Comments on nanoscale views: This week in cond-mat (mini-version + digression)Douglas Natelsonhttp://www.blogger.com/profile/13340091255404229559noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-13869903.post-1160057530406756892006-10-05T09:12:00.000-05:002006-10-05T09:12:00.000-05:00Hi Doug, thank you for featuring our paper. It has...Hi Doug, thank you for featuring our paper. It has been finally published in APL89, 133504 (2006). <BR/>As one of the co-authors of the RMP, I would like to mention a similar work has been also done by another co-author which is seen in a recent issue of Science. The work is independent of our present work, but is rather more similar to my previous work which is included in the RMP. The guys are clever enough to fairly extend my incomplete work... <BR/>However, we are proud that we have also done it in more straightforward fashion, as JHS did five years ago. <BR/>Isao.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13869903.post-1160057423035425232006-10-05T09:10:00.000-05:002006-10-05T09:10:00.000-05:00Hi Doug, thank you for featuring our paper. It has...Hi Doug, thank you for featuring our paper. It has been finally published in APL89, 133504 (2006). <BR/>As one of the co-authors of the RMP, I would like to mention a similar work has been also done by another co-author which is seen in a recent issue of Science. The work is independent of our present work, but is rather more similar to my previous work which is included in the RMP. The guys are clever enough to fairly extend my incomplete work... <BR/>However, we are proud that we have also done it in more straightforward fashion, as JHS did five years ago. <BR/>Isao.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13869903.post-1155667190838016332006-08-15T13:39:00.000-05:002006-08-15T13:39:00.000-05:00Hey Peter - I agree with what you said, and I sho...Hey Peter - I agree with what you said, and I should take a closer look at their hopping parameters. These materials are known to be hopping conductors, though the situation is complicated because the density of (localized) states is strongly energy dependent. The best analogy I can make here is to consider a hot filament at some dc bias relative to a nearby ground plane. As the temperature is reduced, the conductance drops because thermionic emission is suppresed. However, at high enough bias, there is Fowler-Nordheim emission that is temperature-independent. I would never consider this the onset of "metallic" conduction. Depinning would probably be the best way to think about the case at hand.Douglas Natelsonhttps://www.blogger.com/profile/13340091255404229559noreply@blogger.comtag:blogger.com,1999:blog-13869903.post-1155654259976211512006-08-15T10:04:00.000-05:002006-08-15T10:04:00.000-05:00Hey Doug. I have similar reservations about such ...Hey Doug. I have similar reservations about such papers that claim to see a MIT in funny contexts. The terms 'metal' and 'insulator' mean specific things and can only be defined rigorously if you stick to narrow definitions. Otherwise you end up with gobbledygook. I'm not sure which standard this paper meets in that regard.<BR/><BR/>As of course you know, there are other prototypes for dynamic phase transitions (current induced CDW depinning, current induced vortex lattice melting) in CM systems. Could this be seen in such a context?<BR/><BR/>I think the burden of proof then is on the authors here to show that the idea of dynamic MIT even makes sense. We can only define metals and insulators on asymptotically low energy scales and thereby using large bias invalidates these assumptions. If they want to claim such a phenomenon I think they should have started off with a simpler material. I have little doubt that if you took Si:P on the insulating side of its MIT and used large currents you would see enhanced dI/dV at large V. Would this be a 'dynamic' MIT? I don't know, and certainly more work would have to be done before one could so. I do grant that the power law behavior in the conductivity over a few decades is interesting though.<BR/><BR/>One other comment: It strikes me that their Efros Shklovskii T's are unphysically large. Are such #'s typical for polymers like this? They are certainly way way off from #'s in disordered semiconductors in regimes where you could see hopping.Peter Armitagehttps://www.blogger.com/profile/11567089164372083820noreply@blogger.com