This week in cond-mat

I know that it's been a while since I've done one of these. It's not because of a lack of interesting papers on the arxiv; rather, it's been entirely due to my own lack of time. On to a couple of interesting papers from this week....

arxiv:0902.3014 - Miroschnichenko et al., Fano resonance in nanoscale structures
This is an article intended for Reviews of Modern Physics that takes pedagogical, unifying look at Fano resonances, particularly in nanostructures. (I've linked to the version with high-res figures.) A Fano resonance is a particular kind of (in general) asymmetric resonance lineshape that results from interference between, for example, [direct transmission into a continuum of states] and [transmission involving scattering from a resonant level]. The end result is a resonance lineshape that can look like resonant transmission, resonant absorption, and a variety of asymmetric shapes in between. Originally proposed by Ugo Fano to explain phenomena in atomic physics, Fano resonances are all over the place in nanoscale systems. This paper actually gives about as nice a pedagogical description of this physics as you're going to find.

arxiv:0902.3305 - Deshpande et al., Spatially-resolved temperature measurements of electrically heated carbon nanotubes
A major issue in nanoscale electronic transport experiments is the question of dissipation and energy relaxation. By applying a voltage across a nanostructure in a measurement of conduction, one is driving the electronic distribution (which electronic states are occupied as a function of energy or momentum) out of thermal equilibrium. Eventually, the electrons rethermalize, transferring their energy to one another and to the vibrational modes of the material in question. How this happens in detail can be quite complicated, and nonthermal distributions of electrons and vibrations can exist over relatively long distance scales (say hundreds of nanometers at low temperatures). These folks have been able to use scanning Raman microscopy to map out the local lattice temperature of carbon nanotubes as current is passed through them. In this case they are looking at the shift of a particular nanotube vibrational mode, and using that as an effective thermometer. It's a pretty experiment that demonstrates how much we can learn by combining electronic measurements with complementary techniques.