Some recent papers of interest

A couple of recent papers that seem interesting and I need to read more closely:

• This paper in Nature, a collaboration between folks at Ohio University and Argonne, is a neat combination of scanning tunneling microscopy and (synchrotron-enabled) resonant x-ray absorption.  The authors bring an STM tip (an extremely sharp metal tip) down to within a nm of the sample surface, so that electrons can tunnel quantum mechanically from the sample to the tip.  Then bang the sample with x-rays that are resonant with core levels of particular atoms in the sample.  In this case, one sample consisted of iron-containing molecules.  The x-rays could kick electrons out of the iron atoms where they are then detected by the tip, allowing atomic-resolution mapping of the desired atoms.  (It's a bit more subtle than that - see Fig. 2j - but that's basically the gist.)
• This paper in Science is also very cool (arxiv version here).  People are generally used to the idea that photons are quantum objects.  Indeed, photons are often discussed when talking about standard examples of quantum "weirdness".  A 50/50 beam splitter can put a photon in a superposition of going down two different paths, for example.  There is a whole approach to quantum information processing based on these properties.  This new paper demonstrates a beam splitter for individual phonons, specifically surface acoustic waves.  This opens the possibility of a solid-state phonon-based version of that approach to quantum computing.  Very neat.
• Lastly for now, this paper in Nature Materials (arxiv version here) uses STM to look at how superconductivity goes away in a cuprate superconductor as the doping level is increased way beyond the level that optimizes superconductivity.  The decrease in transition temperature and superfluid density with increasing doping has been a mystery.  This paper shows that the system breaks up into superconducting puddles surrounded by metallic regions, and that instead of the superconducting energy gap closing (implying a weakening of the interaction that pairs up the electrons), it "fills in".  Lots to ponder.