Two more papers that look interesting.
arxiv:0706.0792 - Koop et al., Persistence of the 0.7 anomaly of quantum point contacts in high magnetic fields
One of the neatest results (in my opinion) in mesoscopic physics is the appearance of conductance quantization in quantum point contacts, first shown in the late 1980s. The basic idea is simple. Start with a two-dimensional electron gas such as that formed at the interface between GaAs and modulation-doped AlGaAs. Metal gates on top of such a structure can be used to deplete the electron gas in particular places. Two closely spaced gates may be used to create a narrow constriction between two large reservoirs of 2d electron gas. As the constriction width is reduced until it is comparable to the Fermi wavelength of the confined electrons, the conductance through the constriction is quantized (at zero magnetic field) in integer multiples of G0 = 2e^2/h, the quantum of conductance (about 1/(13 kOhms)). That is, each spatial mode (each transverse subband of the constriction) can transport e^2/h worth of conductance per spin degree of freedom. Indeed, at very large magnetic fields, the conductance is quantized as integer multiples of G0/2, as one would expect if the different subbands are spin-split due to the Zeeman effect. This is all well explained by single-particle theory and the Landauer-Buttiker picture of conduction through small systems. In very clean quantum point contacts, additional structure is seen at 0.7 G0 - this is the so-called 0.7 anomaly. In the presence of a little bit of in-plane magnetic field, this approaches 0.5 G0, and therefore looks like there is some spontaneous spin-splitting, and this is a many-body effect that is the result of some kind of electron-electron correlation physics. This paper is an extensive study of 14 such point contacts, fully mapping out their magnetic field dependence and nonequilibrium (large bias voltage) properties.
arxiv:0706.0906 - Clark et al., Nonclassical rotational inertia in single crystal helium
The controversy over whether 4He has a true supersolid phase continues. This week this article appeared in Science, summarizing a number of recent experiments, and strongly suggesting that single crystals of pure 4He should not show a real supersolid phase - basically the claim is that the effects ascribed to such a phase are really due to disorder (glassy 4He at grain boundaries between crystals? 3He impurities somehow?). Now comes this paper from Moses Chan's group, arguing from new experiments that even carefully nucleated and grown single crystals of 4He show evidence of supersolid behavior (in the form of a nonclassical moment of rotational inertia). Hmmm. Neat, clever experimental design. It'll be interesting to see how this all pans out.