APS March Meeting 2026, Day 2

Today was again a bit random, as I had talks for both one of my students and me, and meetings with folks.  Some highlights:

• Edoardo Baldini gave a very nice talk about exotic phases and collective excitations in van der Waals magnets.  This included using second harmonic generation microscopy and polarimetry to look at the evolution of magnetic phases in NiPS3 as a function of thickness, ending up at the monolayer which acts like a 2D XY magnet.  In the paper, they see clear evidence of a BKT transition, plus a second lower temperature ordering of some kind.
• After some AV issues (seem like quite a few of those this year), Barry Zink gave an interesting presentation about using Cr as a spin detector in spin Seebeck measurements on YIG, and looking at how the antiferromagnetism of the Cr affects the measurement (see here).  In new results, they have been adding in an intervening layer of antiferromagnetic IrMn, looking at how magnons in the IrMn affect the results.
• This was followed by a talk by Romain LeBrun all about spintronics in the GHz and THz, using hematite (Fe2O3) as an example antiferromagnetic insulator.  They see some interesting nonlinear dynamics and rectification in antiferromagnetic resonance in Fe2O3.  In NiO, they use optical excitation to drive coherent phonons, exciting a spin current, which then leads to a THz pulse when the spin current hits an inverse spin Hall detector (Pt or W).  Similar experiments in BiFeO3 show that THz generation in that multiferroic system can arise just from oscillating the ferroelectric polarization.
• Andrew Dane from IBM gave a great presentation to a more-than-packed room about their recent studies of two-level systems in qubits.  From waaaaay in the back, I learned about their use of nearby suspended electrodes to apply electric fields to try to shift the energies of some of the TLS (the ones with electric dipole moments and at the surface of the devices).  TLS drastically suppress the coherence of superconducting qubits, and understanding their origins and ways to work around them (to characterize fab processes, for example) is very important.  As I said in that post linked above, once again we see that TLS are everywhere, and they are evil.  I need to think about whether there's anything I could contribute on this.  The real highlight of the talk was the use of "percussive maintenance" (banging the side of the cryostat) to alter the not-field-tunable TLS distribution via some unknown mechanism.
• Bonking the experiment was taken to a new level in this talk about mechanoluminescence, which involved shooting the sample with an airsoft pellet gun under controlled conditions.

There were other talks as well - some fun stuff.  I also want to give a shoutout to the free-to-play vintage arcade games in the exhibit hall.  Galaga and the stand-up vector graphics Star Wars game were great consumers of my time and my quarters back in the day.