Thursday, May 28, 2009

Random tidbits

Several minor things....
  • I've got an article on single-molecule electronics coming out in the June issue of Physics World. It's reasonably accessible, and I'm pretty happy with how it turned out, though I wish there had been more space to discuss the theoretical challenges.
  • This is damned cool. I had an undergrad course that was like the baby version of this - building up transistors into logic gates; then using logic gates to build a shift register; then building and programming a little 6502-based computer to run a model train network. This guy's work puts all that to shame by comparison.
  • The pseudonymous Kyle Finchsigmate, always entertaining and clever (often profane), has started a wiki site devoted to chemistry experimental techniques. In comments about that I came across this site from Rochester. I think it would be great to have a site like this about experimental physics, though clearly it would take a lot of work from many people to have it be any good....
  • I've been asked by a reader to solicit discussion and opinions about the various journal online manuscript submission/review systems. Which ones are good, and which ones are lousy? From what I can tell, the APS system is decent (though it always seems to complain erroneously about mistakes in my references and article lengths), and the Paragon system from ACS is quite good. The Nature publishing group one also seems to be put together well. I'm not a fan of "Manuscript Central" or whatever it is that Elsevier and IEEE use. What do you all think?
  • Thank goodness McLeroy was not confirmed as head of the TX board of education.
  • This'll be the last update for about the next 9 days or so, since I'll be traveling with very limited 'net access.

Tuesday, May 26, 2009

Plastic Fantastic thoughts

Reading Eugenie Reich's Plastic Fantastic brought me right back to the heady days of my postdoc, job search, and nearly a year spent with a student chasing what turned out to be fabricated results. In hindsight I learned an awful lot about human nature and the sociology of science, and some of that is conveyed to readers of this book, though not all.

First, the book review. I think Reich writes well, and I think she did a good job simplifying the science where appropriate for a more general audience. Criticizing the details (e.g., I wasn't a big fan of her definition of "polaron") misses the larger point (you don't need to know what a polaron is to appreciate the fact that Schon didn't fully get what polarons are either). Personally I think it would have been useful to spend more time on standard scientific practice at Bell Labs - Schon's claims (going back to his doctoral work in Germany) that he didn't keep notebooks or save primary data aren't just damning - they're completely outside what I saw essentially everyone else do, both at Bell and in grad school. How on earth did this happen? How did no one immediately supervising Schon never notice that he had no notebooks?! The idea that researchers at Bell were so independent that no one would ever notice this is crazy. I also think it would have been good to spend a bit more time on the denoument, at least discussing further the major issues raised by this whole affair: what are the responsibilities of co-authors? What are the responsibilities of managers? There were also some nuances of what happened as the scandal broke that I didn't see (though I could've missed them on a quick read), including some choice remarks by Batlogg that were rather remarkable at the time. [One other point: Reich points out that the Departments of Defense and Energy don't have central offices of research integrity. Strictly speaking, that's right, but the way it's written makes it sound like DOD and DOE never even consider the matter, which is not true. Since 2000, anyway, DOE has used the following (pdf) policy regarding research misconduct, which is basically the blanket federal policy applied at DOD as well.] In the end, the book is very effective at what it does, though it raises many more questions than it answers.

Regarding specific comments of others.... I don't think management was dealt with unfairly here in general. I didn't feel like Cherry was particularly singled out. Also, the book doesn't convey well one factor that I think is important to remember: most of the immediate managers (e.g., Rogers, Capasso) were running large, active research programs of their own. There's no question that between that and the corporate turmoil from the collapse of telecom, these people had other things on their minds than trying to manage Schon. Now, that being said, how in the name of all that is holy did these people not realize that Schon's publication rate was simply unphysical? NO ONE can write a paper every two weeks for two years. Didn't this raise questions at the journals, too? One other comment about management that was raised only indirectly.... There were a number of people who were thrilled to claim (effectively) some share of the credit for this stuff when things looked good, but were quick to disavow all responsibility when things went bad. You can't have it both ways.

(One final point that has nothing to do with the author: the choice to put a silhouette of Icarus on the cover is deeply flawed. Icarus actually flew.)

Saturday, May 23, 2009

Anyone read this yet?

I was in Barnes & Noble yesterday evening and saw a copy of Plastic Fantastic in their science section. This is Eugenie Reich's telling of the Schön saga. Anyone out there had a chance to read this yet? Steve? Don? I'll have to pick up a copy at some point.

Tuesday, May 19, 2009

Wolfram|Alpha: not too impressive.

By now many of you have run across Wolfram|Alpha, billed by its creator as a "computational knowledge engine". I've been goofing around with it a little over the past two days, and I'm not too impressed, though there are some cute things in there. The demonstration video, narrated by Wolfram himself, is very slick, and gives you the impression that Wolfram|Alpha can take even minimalistic requests (e.g., "Germany US GDP") and provide lots of computed output (US and German GDPs side by side as a function of time, in various different currency units and normalizations, for example). That is sort of true, for a very limited subset of queries. As one might expect from the people who developed Mathematica, Wolfram|Alpha can also do some symbolic math, including graphing of functions.

Unfortunately, it would appear that their model is to have these kinds of limited queries templated by hand on their side. Trying to ask well-defined questions about comparatively simple things ("What is the resistance of a wire?"), which you might expect from the demo to call up a pretty set of dialog boxes, etc., instead gives you "Wolfram|Alpha isn't sure what to do with your input." In this particular example, just "resistance of a wire" calls up dialog boxes about US and UK wire gauges and is at least somewhat useful. For a parser to do fine with "resistance of a wire" and gag on "what is the resistance of a wire" is pretty sad these days.

Bottom line: the idea of Wolfram|Alpha is cute, but right now it's entirely too much like playing an old text adventure game:
You are facing a brown, wooden door set in a dark green frame. There is a doorbell button here.

>Ring the doorbell.

I do not know how to do that.

>ring doorbell

I do not know how to do that.

>push button

You push the button, and from within the house you hear a distant chime.

Wednesday, May 13, 2009

Faking APS email not a good way to be taken seriously

Many of us know the joy of getting email from, err, enthusiastic amateurs claiming to have solved all of the great problems of modern physics (often involving the invalidation of quantum mechanics, relativity, or both). This morning's allotment was particularly amusing, though. Subject line: Giant Revolution in the Physics Science. From: [allegedly] (Really from someone in Hungary.) It explicitly claims to be a message on behalf of about a dozen physicists (presumably not with their actual permission), including last year's Nobel Laureates. Even better, it asks us all to contact the Royal Swedish Academy (complete with contact information) and pressure them to award the Nobel in physics to a Hungarian physicist who "reinterprets the total known experimental results and uses solely the mathematical apparatus of dynamics and electrodynamics". Amateurishly spoofing email from people is no way to promote yourself....

Tuesday, May 12, 2009

This week in cond-mat

Two recent arxiv papers caught my eye. I'm not working on graphene, but these are both pretty interesting results.

arxiv:0905.0923 - Mak et al., Observation of an Electric-Field Induced Band Gap in Bilayer Graphene by Infrared Spectroscopy
The authors, from Tony Heinz's group at Columbia, make a field-effect device out of bilayer graphene (identified optically thanks to its particular Raman spectrum) and an electrolyte. As I'd mentioned once before, by using electrolytes it is possible to achieve very large gated charge densities in transistor-style devices. In this case, the authors find that they can turn bilayer graphene from a semimetal-like system (with touching valence and conduction bands at the charge neutrality point) to a semiconductor (as determined via optical measurements), with a band gap induced and controlled by the gate. I need to read more carefully just how this works, but it shows how these kinds of experiments (moving a good fraction of a charge per unit cell around) can alter band structure profoundly.

- Li et al., Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils
This paper, published this week online in Science, may end up being quite important. The authors show that they can grow mostly single-layer graphene on copper supports. Copper can be annealed to produce large (several mm) crystallites, so significant areas of graphene can be made this way, templated with comparatively few defects. The big step here compared to earlier work on growing graphene using Ru or Ni substrates is that the resulting material seems to be self-limiting in thickness because of the mutual solubility limits of C in Cu and Cu in C. The authors can also transfer the graphene to other substrates, including Si chips, a necessary step for any would-be electronics applications.

Saturday, May 09, 2009

Star Trek

I saw the new Star Trek movie last night, and it was extremely fun. Great special effects, with nods to all the appropriate elements of the original series. I also loved the score - Michael Giacchino rocks. (Sorry for the wiki link - his website seems to be down.) Sure, the science can be goofy, and the plot has some flaws, but somehow it really felt like old-school Trek in all the right ways.

Talks in 90 seconds

At the workshop I'd mentioned, because of time constraints only 11 of the participants had the chance to give full talks. To try to get a better sense of what everyone else was working on, the organizers let anyone else who wanted to speak give a 90 second talk after dinner on the first night. This was a fascinating exercise, taken in good fun by all involved. The time limit was enforced by a big analog timer with a loud buzz.... As you might imagine, conveying what your group is doing given just 90 seconds is a challenge. About 19 people tried this, using anywhere from one to ten (!) powerpoint slides. It worked surprisingly well, actually. A neat idea.

Thursday, May 07, 2009

The workshop experience

I just finished attending a three-day workshop near Washington, DC sponsored by the National Nanotechnology Initiative (and other "participating agencies", since technically the US Department of Defense is not strictly part of the NNI, for reasons which escape me), focused on "nanotechnology-enabled sensing". Since I've only backed into anything sensing related in the last couple of years, this was very educational for me. The workshop was put together, in part, by Roger van Zee from NIST and Gernot Pomrenke from AFOSR, and was tasked with producing a report on the topic. The report is actually supposed to be useful to diverse a diverse audience, from technical contacts at the various agencies to Congressional staffers and the White House Office of Science and Technology Policy. I learned a lot, and met many interesting people from other universities, national labs, industry, and federal agencies.

As you might imagine, producing the report is quite a task. You have to corral 30-40 PhD researchers (who all have their own areas of expertise and writing styles), and build up a consensus document that is comprehensive, readable, brief but with some technical depth, and covers an extremely broad topic. Sensing is particularly tricky, since there are many many transduction mechanisms, many many things that people want to detect (including small molecule chemicals, biomolecules, cells, physical variables, EM radiation), and lots of ancillary requirements (biocompatibility? specificity? portability? low power?). It's like herding cats, but in the end I think this report should do a good job of highlighting what nano can do for sensing. (Here's the five-word executive summary: Sensors good, nanosensors much better. See? Who says that it's tough to write for non-scientists....)

Sunday, May 03, 2009

Small really is different

Shameless self-promotion part II. The actual scientific result that just came out in Nature is rather surprising. There are two "ordinary" settings for Kondo physics: a magnetic impurity in an otherwise nonmagnetic host (e.g., dilute Mn atoms in Cu), or a quantum dot containing an unpaired electron. In the former case, the conduction electrons of the host metal can lower their kinetic energy by trying to occupy a singly occupied d orbital of the magnetic impurity. However, because of the Coulomb repulsion of the other electrons on the impurity atom, really doing this is classically forbidden by energy conservation. Still, quantum mechanics lets that forbidden state exist as a virtual intermediate state in a scattering process that takes a conduction electron from the host, flips the spin of the impurity atom, and spits out an electron into a different conduction band state. In the quantum dot case, an analogous magnetic dance takes place, in which the spin of the unpaired electron on the dot is flipped, and an electron is transferred across the dot. This Kondo scattering process affects the electronic conduction through the dot in a particular, identifiable way.

The surprising result in our case is that we see indications of this Kondo process in atomic-scale junctions between chemically homogeneous (e.g., all the atoms are Ni) ferromagnetic metals. The data are pretty clear, and indicate that this spin-related process competes with ordinary ferromagnetic exchange in these nanostructures. It would appear, from accompanying theory calculations by our coauthors, that the very act of whittling the ferromagnetic metal down to the atomic-scale junction is enough to mess with the electronic properties of the metal that we'd ordinarily consider to be intrinsic. The bottom line is, when worrying about the magnetic properties of truly nanoscale structures (with many surface atoms), one may need to keep track of relatively exotic ("strong correlation") physics like the Kondo effect.