APS March Meeting 2022, Day 4 and wrap-up

I gave my contributed talk this (Fri) morning, and I will head to the airport shortly, so this is the end of my March Meeting blogging.  A few highlights from yesterday:

• Konrad Lehnert gave a very nice, pedagogical talk about the possibility of detecting axionic dark matter using quantum sensing.  The super short version:  it is thought that axions if they exist can, in the presence of a large magnetic field, convert at some rate into photons with energy \(\hbar \omega = m_{\mathrm{a}}c^2\).  In a microwave cavity, it is possible to detect such excess photons, and by doing clever things with "squeezing", it is possible to beat the standard quantum limit and to examine parameter space more rapidly than otherwise.  There is still a lot of room for improvement if one wants to be able to look across the whole range of potential axion masses and not have it take years and cost a gazillion dollars.  One approach using entanglement can eliminate a number of confounding factors.
• I saw two very clear talks, one by Kevin Nuckolls and one by Stevan Nadj-Perge about using STM and tunneling (and point contact) spectroscopy to examine superconductivity in magic-angle twisted bilayer and trilayer graphene, respectively.  In the former, one challenge is to decide how much of the observed gap features in tunneling are due to superconductivity, and then using the functional form of that superconducting part to consider pairing mechanisms.  It is also possible to see how band flattening increases the density of states even at angles away from the magic angle.
• In a different session, Inti Sodemann spoke about whether and how it is possible to get current rectification in semiconductors when they are illuminated by light with energy below the band gap, so that there is no absorption.  There are thermodynamic restrictions that come in - you can't get energy from nowhere, and you can't break the second law.  Thanks to Berry curvature effects, it is actually possible to have this kind of rectification under some circumstances.
• There was another extremely clear talk by N. Peter Armitage about Co-containing compounds as Kitaev spin liquid candidates.  There was some really great THz absorption data as a fn of temperature and magnetic field for CoNb2O6 that had amazing agreement with theory, and newer results looking at a more 2D system, BaCo2(AsO4)2.
• Unfortunately I was unable to attend the Kavli Symposium.  I hope to be able to watch the talks later, as these are typically of very high quality and general interest.

Closing thoughts:

• It was nice and kind of weird to finally see a good number of people in person.  Really great to catch up with old friends, though I think my conference stamina has waned since the 2019 meeting.
• When the participants skew younger, as seemed to be the case this year, the crowd definitely looks more diverse.  It would be interesting to know the demographics of the attendees.
• I don't think pre-recorded short talks work well.  The inability to ask/answer questions is a problem.  
• I wonder if we will have hybrid meetings in general from now on.  There are definitely environmental impact reasons to go that way, and it would help solve the APS's problem that prior to covid the meeting had grown so large that it was difficult to plan or host.