Wednesday, March 06, 2019

APS March Meeting Day 3

A handful of semi-random highlights (broken up by my conversations w/ colleagues and catching up on work-related issues):

  • Laura Heydermann from ETH spoke about "artificial" magnetic systems, where mesoscopic, lithographically patterned arrays of magnetic islands can yield rich response.  A couple of representative papers are here and here, and recently they've been moving into 3D fabrication and magnetically sensitive imaging.  Very neat stuff.  
  • Christian Glatti from Saclay showed a very interesting result, analogous to the ac Josephson effect, but in fractional quantum Hall edge-state tunneling.  The relevant paper, just out in Science, is here.  This idea is, measure electronic shot noise as a function of bias voltage.  Ordinarily this has a minimum at zero bias, and the noise sits at the Johnson-Nyquist level there.  Now shine microwaves of frequency f on the device.  With photon-assisted tunneling, the net result is a change in the noise that has kinks at voltages of +/- hf/e*, where h is Planck's constant, and e* is the effective charge of the low-energy excitations.  Do this in the fractional quantum Hall regime, and you see fractional charge.  
  • On a related topic, Michael Pepper from Cambridge showed a very recent result.  In quantum point contacts at very low charge carrier densities, they see quantized conductance at some very surprising rational fractions of the usual conductance quantum 2e2/h.  I still need to digest this.  
  • I spent much of the afternoon at the big Kavli Symposium, on topics spanning from unit cell all the way to biological cells.  All excellent speakers.  I won't try to summarize this - rather, when the talks become available streaming, I will put the link here.  (Claudia Felser did bring donuts for the audience to talk about topology, always a crowd-pleaser.)

No comments: