## Tuesday, September 12, 2017

### DOE experimental condensed matter PI meeting, day 1

I'm pressed for time, so this is brief, but here are some things I learned yesterday:
• An electric field perpendicular to the plane can split and shift the Landau levels of bilayer graphene.  See here.
• The quantum Hall effect in graphene and other 2d systems still has a lot of richness and life in it.
• I have one word for you...."polaritons".
• It's possible to set up a tunneling experiment, from one "probe" 2d electron gas that has a small, tight Fermi surface, into a "sample" 2d electron gas of interest.  By playing with the in-plane magnetic field, the tunneling electrons can pick up momentum in the plane as they tunnel.  The result is, the tunneling current as a function of voltage and transverse fields lets you map out exactly the "sample" electronic states as a function of energy and momentum, like ARPES without the PES part.  See here.
• Squeezing mechanically to apply pressure can actually produce dramatic changes (quantum phase transitions) in unusual fractional quantum Hall states.
• How superconductivity dies in the presence of disorder, magnetic field, and temperature remains very rich and interesting.  The "Bose metal", when magnetic field kills global phase coherence without completely ripping apart Cooper pairs, can be an important part of that transition.  For related work, see here.
• One should be very careful in interpreting ARPES data.  It's entirely possible that not everything identified as some exotic topological material really fits the bill - see here.  On the other hand, sometimes you do see real topologically interesting band structure.
• The DOE still has laptops running Windows XP.