APS March Meeting, day 3

(Note that I'm leaving out the parts of the meeting where I did things like chat with friends and colleagues, and visit the trade show - I doubt anyone wants to read that stuff.)

I started day 3 with some plasmonics talks.  A particularly remarkable piece of work was presented by Teri Odom, discussing her group's plasmonic lasing efforts.   Metal nanoparticles excited at their local plasmon resonance can support very large local enhancements of the electromagnetic field, effectively confining light to incredibly small, sub-wavelength volumes.  However, usually the plasmon modes are relatively broad, so that a photon doesn't "live" very long in those tiny volumes.  By combining many nanoparticles in a regular array, the interparticle coupling can lead to a collective, coherent narrowing of those resonances.  When combined with a gain medium (in this case IR-140, an infrared dye with emission commensurate with the resonance of the metal nanoparticle array), the result is an optically pumped laser, with emission that can be tuned across the dye's bandwidth by changing the index of refraction of the surrounding medium.

I then tried to learn about Weyl fermions. This is another example of a particle originally proposed in the high energy physics context, with some peculiar relationships between energy, momentum, and angular momentum, and then seen in the emergent properties of a condensed matter system.  Truth be told, the talks I saw focused much more on the photoemission techniques, materials, and the steady stream of high profile publications than on providing a pedagogical approach to these funky (quasi)particles.

Eli Yablonovitch gave a fun, informative Buckley Prize talk, on the history of photonic band gap systems and their use to engineer spontaneous emission, optical antennas, and lastly structural color in nature.  Regarding optical antennas, he argues strongly that it's useful to think of these things in the context of classical antenna theory (basically modeling the antenna as an equivalent circuit made from discrete inductors, capacitors, and resistors) rather than other approaches involving quantum optics concepts.  I'm sure he's right in many cases, but fundamentally it seems to me that lumped element models can't really work well when worrying about a number of problems.

Nadya Mason gave a compelling talk about the nature of superconductivity in islands of granular Nb, as a test case to better understand the low-T metallic state of many thin systems in which superconductivity can be suppressed.  It's elegant work gaining new insights into a classic problem.  Many aspects can be explained with a simple model involving the distribution of grain sizes (and hence local superconducting transition temperatures), though mysteries remain, such as how nearby islands coupled by a normal metal film really talk to each other.

After a fun lunch with blogger extraordinaire Chad Orzel, I heard Yong Chen from Purdue present his group's work on transport in small devices made from 3d topological insulators of sufficiently high quality that the bulk is actually insulating, like it's supposed to be.  The favorite materials are apparently BiSbTeSe₂, which can be exfoliated from bulk or grown in film form, and vapor-grown nanowires of Bi₂Te₃.  That work is here and here, respectively.

After some talks on VO₂ (it's still complicated), I rounded out the day by going to the end of the Kavli Frontiers symposium.  My colleague Naomi Halas gave an extremely impressive talk about plasmonic particles for heat transfer and steam generation, and this was followed by an exhuberent lecture from Duncan Brown, who presented the LIGO gravitational wave detection experiment.  His excitement and joy about the result were infectious.

Next:  my last half-day of the meeting, + final thoughts.