Sunday, March 18, 2007

This week in cond-mat

A few highlights from this week, though brief. I've actually been working on my book rather than writing as much. Coming soon: more about faculty searches (now that I don't have to worry that my comments could give an unfair advantage to any candidate, since we're past the interviewing stage).

cond-mat/0703230 - Karabacak et al., High frequency nanofluidics: an experimental study using nanomechanical resonators
With my mech-E background, I've always liked fluid dynamics and lamented that it gets left out of the typical physics curriculum. This is a nice use of nanomechanical resonators as a means to study fluid motion via the resulting damping of the resonator. Of particular interest is the transition between Newtonian flow (shear stress on a wall given by the product of a viscosity times the velocity gradient at the wall) and non-Newtonian flow (shear stress depending on shear rate, for example; cornstarch in water gets stiff at high shear rates, while mayonnaise gets softer at high shear rates. Both are non-Newtonian fluids).

cond-mat/0703374 - Katsnelson and Novoselov, Graphene: new bridge between condensed matter physics and quantum electrodynamics
This is a good, pedagogical review of a lot of the interesting physics seen in electronic transport in graphene. Because of its band structure, electrons and holes in graphene act rather like ultrarelativistic particles (that is, their energy is approximately linearly proportional to their (crystal) momentum, like photons). The discussion in this paper of the Klein paradox is particularly nice; I hadn't read such a clear summary of it before.

cond-mat/0703247 - Malyshev, DNA double helices for single molecule electronics
This has already come out in PRL. While I'm sure the calculations are reasonable and robust, this is a classic example of a theory proposal that is much easier to talk about than ever actually try. My main problem here is that actually preparing electronic devices from DNA and ending up with a controlled system is incredibly hard. There are compensating ions all over the place; DNA in vacuum or on a surface is not nearly the same thing as in a biological environment, including its conformations. Ahh well.

cond-mat/0703419 - Zhang et al., Noise correlations in a Coulomb blockaded quantum dot
Yet another pretty piece of experimental work from Harvard and Tokyo. Using a combination of tank circuits (RLC resonators), cold voltage amplifiers, and a cross-correlation system, these folks are able to measure shot noise in a Coulomb-blockaded quantum dot. They can use a gate to tune the dot in and out of blockade, and can watch the noise vary from sub- to superPoissonian (that is, are the electrons behaving independently (Poisson statistics for tunneling), avoiding each other (sub-Poissonian), or bunching (super-Poissonian). It all looks so easy, though I know experiments like this are very challenging.


Anonymous said...

Another nice summary of graphene physics by Geim and Novoselov is in the recent issue of Nature Materials (here). I noticed a number of mainstream articles referencing this paper when talking about developments in graphene nanoribbon transistors - they seem to be referencing fig. 6. Do you happen to know anything about the current status of the actual nanoribbon transistor paper ("L.A. Ponomarenko, F. Schedin, K.S.N. & A.K.G., in preparation", according to the caption of fig. 6)?

Unknown said...

Thanks for the nice words, Doug.