Friday, March 14, 2008

March APS Meeting wrapup

I returned yesterday evening from the March Meeting, and spent much of today helping out with our graduate recruiting weekend for both my department and the applied physics graduate program. Hence the delayed blogging.

My last day at the March Meeting was spent largely flitting from session to session. I saw a very nice pair of talks by David Cobden and one of his students from Washington, showing measurements of the metal-insulator transition in VO2 nano-beams. Vanadium dioxide is allegedly a Mott insulator in its low temperature state, meaning that the on-site repulsion of the d orbitals of the vanadium is so strong and the electronic population is just right so that the whole correlated system is frozen. A bit above room temperature (around 65 C) VO2 becomes metallic, and there's been a lot of interest in understanding the transition, which is accompanied by a lattice distortion. In the new work, suspended beams of the oxide are observed in an optical microscope while the transition is examined. There is optical contrast between the two phases, so one can determine how much of the beam is in each phase in the coexistence region. Moreover, the elastic properties of the beam allow them to infer much information about the phase diagram for the transition, and offer some hints in conjunction with conductance measurements that the metal/insulator transition may be separate from the structural transition.

After this, I went off to the session on charge and orbital ordering to give my own talk about our magnetite results. Then I headed over to a session on molecular electronics. Finally, I ended up over near a focus session on nanotechnology, where there were a couple of nice talks on fabrication methods.

Overall, it was a good meeting - as good as these things usually are. Most of the talks that I saw were pretty decent, and I had some useful conversations with lots of colleagues. Only once or twice did it occur to me that sessions could be more pleasant if someone replaced the usual oven timer for pacing talks with either a giant gong or perhaps one of those big hooks used to pull people off stage in bad vaudeville skits.

1 comment:

David Cobden said...

Hi Doug,

Thanks for the nice comments about our talks! For anyone who is interested, I'd like to add that the most surprising result we got was that the resistivity of the insulating phase is independent of temperature if you move along the metal-insulator phase boundary in VO2, implying that the transition occurs at a particular carrier density, just as I think would be the case for a Mott-Hubbard transition.

It continues to amaze me how you manage to keep this blog and do so many other things.

Dave