DOE Experimental Condensed Matter Physics PI Meeting 2015 - Day 2

Among the things I learned at the second day of the meeting:

• In relatively wide quantum wells, and high fields, you can enter the quantum Hall insulating state.  Using microwave measurements, you can see signatures of phase transitions within the insulating state - there are different flavors of insulator in there.  See here.
• As I'd alluded to a while ago, you can make "artificial" quantum systems with graphene-like energetic properties (for example).  
• In 2d hole gasses at the interface between Ge and overlying SiGe, you can get really huge anisotropy of the electrical resistivity in magnetic fields, with the "hard" axis along the direction of the in-plane magnetic field.
• In single-layer thick InN quantum wells with GaN above and below, you can have a situation where there is basically zero magnetoresistance.  That's really weird.
• In clever tunneling spectroscopy experiments (technique here) on 2d hole gasses, you can see sharp inelastic features that look like inelastic excitation of phonons.  
• Tunneling measurements through individual magnetic nanoparticles can show spin-orbit-coupling-induced level spacings, and cranking up the voltage bias can permit spin processes that are otherwise blockaded.  See here.
• Niobium islands on a gold film are a great tunable system for studying the motion of vortices in superconductors, and even though the field is a mature one, new and surprising insights come out when you have a clean, controlled system and measurement techniques. 
• Scanning Josephson microscopy (requiring a superconducting STM tip, a superconducting sample, and great temperature and positional control) is going to be very powerful for examining the superconducting order parameter on atomic scales.
• In magnetoelectric systems (e.g., ferroelectrics coupled to magnetic materials), combinations of nonlinear optics and electronic measurements are required to unravel which of the various possible mechanisms (charge vs strain mediated) generates the magnetoelectric coupling.
• Strongly coupling light in a cavity with Rydberg atoms should be a great technique for generating many body physics for photons (e.g., the equivalent of quantum Hall).
• Carbon nanotube devices can be great systems for looking at quantum phase transitions and quantum critical scaling, in certain cases.
• Controlling vortex pinning and creep is hugely important in practical superconductors.  Arrays of ferromagnetic particles as in artificial spin ice systems can control and manipulate vortices.  Thermal fluctuations in high temperature superconductors could end up limiting performance badly, even if the transition temperature is at room temperature or more, and the situation is worse if the material is more anisotropic in terms of effective mass.
• "Oxides are like people; it is their defects that make them interesting."