Intriguing papers - exquisite thermal measurements + automated materials discovery/synthesis

It's a busy time, but I wanted to point out a couple of papers from this past week.

First, I want to point to this preprint on the arxiv, where the Weizmann folks do an incredibly technically impressive thing.  I'd written recently about the thermal Hall effect, when a longitudinal heat current (and temperature gradient) in the presence of a magnetic field results in a transverse temperature gradient as well as the usual longitudinal one.  One of the most interesting ways this can happen is if there are edge modes, excitations that propagate around the perimeter of a 2D system and can carry heat (even if they are neutral and don't carry charge).  Unsurprisingly, to measure thermal transport requires putting thermometers at different places on the sample and carefully measuring temperature differences.  Well, these folks have done just exquisitely nice measurements of Johnson-Nyquist noise in particular contacts for thermometry, and they can see the incredibly tiny heat currents carried by rather exotic edge modes in some unusual fractional quantum Hall states.  It's just a technical tour de force.

Second, on a completely unrelated note, there are back to back papers in Nature this week from the Google deep mind folks - their own write-up is here.  The first paper uses their methods to predict a large number of what are expected to be new stable crystal structures.  The second paper talks about how they used an automated/robot-driven lab to try to synthesize a bunch of these in an automated way and characterize the resulting material.  This is certainly thought-provoking.  It is worth noting that detailed characterization (including confirming that you've made what you were trying to make) and optimized synthesis of new materials is very challenging and of concern here.  Update:  there is further discussion of the characterization here (on LinkedIn by the authors) as well, and more on Twitter here and here.

Third, this paper looks extremely interesting.  It’s long been a staple of condensed matter theory to try to capture complex materials with effective low energy models, like suggesting the Hubbard model as a treatment of the essential physics of the cuprate superconductors.  The authors here report that they’ve done a more orbital-based/ab initio version of this, solved these models numerically, and state that they can reproduce details of the phase diagram of four of the cuprates spanning a big range of superconducting transition temperatures.  Seems like this may bode well for gaining insights into these systems.