Friday, March 22, 2013

APS March meeting, day 4 (and wrapup for me)

Due to the constraints of real life, the March Meeting was over for me yesterday afternoon, but I did see a few more interesting talks.

In the morning, I went to the session about valley polarization in transition metal dichalcogenides That's quite a mouthful, and demands some explanation.  In a number of materials (including dichalcogenides like MoS2), the conduction band has more than one energy minimum (or valley) as a function of electron momentum.  In MoS2, there are two energetically equivalent valleys.  Achieving "valley polarization" refers to exciting electrons in only one of those valleys.  Why would you care?  Well, any way of labeling your charge carriers is potentially a means of storing and manipulating information.  In materials like these but possessing broken inversion symmetry (that is, the material has a built-in directionality due to its structure), it is possible to do clever things with circularly polarized light to populate a valley preferentially.  In materials with strong spin-orbit coupling, it is then possible to manipulate spin through valley selection, etc.  The talk by Wang Yao did a very clear job of explaining all this pedagogically, and later talks in the session were also good.

I tried to check out an invited talk on resistive memories, but the chair had let the session fall 15 minutes behind schedule in the first hour.  Note:  there is a reason for timers, and if you're going to be a session chair, you have to hold people to their allotted slots.

I did make it to John Martinis' talk about whether materials are good enough to build a superconducting quantum computer.   It sounds like there is cause for cautious optimism, but wow is it going to be a difficult engineering task.  I need to look up how surface coding is supposed to work.

Finally, I finished off my time at the meeting by going to a session on science and public policy.  Unfortunately this was a depressing way to leave things, since the general message in the end was that Congress is truly dysfunctional, with little hope for any bipartisan support for science - in part because of reflexive opposition, and in part because a significant fraction of the Republican base literally does not believe that science is a valid tool for shaping policy.

One final note for the APS planners in future years:  Please make sure that the APS webserver for the meeting site can actually handle the load.  Still, all in all, a good meeting.

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