Copasetic Flow

I'm reading through the following in preparation for writing a (hopefully) simplified summary of the electron-hole theory of superconductivity.  For those who would like to follow along, each of the references below i a great resource targeted at different experience levels. 1.    +Jonah Miller 's article on band structure as it relates to how materials conduct electric charge [1].  This is a great starting point for the lay-audience.  Jonah is great at explaining physics at any level by the way!  He recently walked Elaine and I through the rudiments of lattice gravity calculations over alcoholic slushies at the  +APS Physics  April meeting. Photo Credit  +Jonah Miller   2.  Dr. Likharev's, (of Stony Brook University), Quantum Mechanics I notes relating to the same topic, but from the point of view of Bloch's theorem.  These are targeted at the physics graduate student reader.  His notes show how the unallowed r...

Watching the Alfred Leitner film on superconductors brought up quite a few things I didn't fully understand about the energy gap of superconductors. I frequently run into a problem when reading physics books and articles and especially when watching physics lectures.  If the writer/presenter doesn't outline in broad details where they're headed, a few deleterious, (for me), effects ensue.  First, I'm likely to lose interest altogether.  Second, since I don't know what the point of the discussion is I usually fail to grasp the few key facts that are embedded within.  This has happened each of the several times I've set out to learn or be taught the details of the energy gap in superconductors.  The same thing almost happened again as I watched Leitner's lecture on the subject, (video excerpt below).  Consequently, I thought it might be handy to provide  a bit of an outline of the key points in the explanation if, like me, you'd rather know where you...

My review of the material I mentioned yesterday [1] paid off pretty quickly.  Dr. Hirsch is quick to point out that one of the key differences between his 'hole theory of superconductivity'[4] and the more typical explanation of Cooper pair formation is that his theory predicts kinetic energy lowering after two holes in an energy band pair as opposed to the usual potential energy lowering after two electrons pair . While reading Hirsch's articles, I didn't remember ever coming across kinetic energy lowering pairing before.  It turned out that I had read about it in Dr. Likharev's notes , (see section 2.6, 'Coupled Quantum Wells'), but without an immediate application for the information, I promptly forgot it. Here are the basics 1.  Crystalline materials, (like superconductors, or semiconductors), in which electrons reside can be very roughly modeled as repeated delta function wells, (picture 1)[2] where the delta functions represent the potentia...

Summary: The photomultiplier tube on the NaI detector doesn't seem to be doing quite what it should.  There's a generally held belief, (when I say generally held belief, read, "a professor told me"), that the count rates aren't high enough.  Last week, the case of the tube was arcing to my hand making nice little static shock looking flashes of light.  Consequently, I spent today doing research on the three most likely PMT tubes that are housed within the detector.  Since the tube is surrounded by a mu metal magnetic shield, it can't be inspected to find it's exact type.  I have a call in to the company that purchased the original manufacturer, and hopefully they can figure out which kind of tube we have.  In the mean time, I've turned down the tube bias which seems to have stopped the arcing.  I've also inspected the voltage divider that provides the accelerating potential for the dynodes in the PMT.  This inspection could just as easily have s...