One last post about hype

...and then I'll get back to science. The pending announcement of the Nobel Prizes in physics and chemistry next week should provide some good fodder for discussion, as well as more arxiv stuff.

Anyway, there was an interesting article in yesterday's Wall Street Journal about the meaning of the word "breakthrough" and its overuse in technology company press releases. Take a look - it's interesting, and confirms what many of us already knew: far more incremental work is being sold as "breakthroughs" now than in the past. The same is true in science as well, though we don't do it to bump up the share price; we end up doing it because the cultural pressures to put out a press release with each publication are seemingly always increasing.

Great subject line

You know you're dealing with a serious, high quality scientific journal when the publisher spams basically anyone who's ever reviewed an article for any of their publications to advertise the journal. For example, I laughed out loud this afternoon when I got an email from Wiley Interscience with the subject line: Reasons You Should Be Publishing In Aggressive Behavior . Hee hee. Maybe the email was misaddressed and was supposed to go to Angry Physics.

Statement on scientific integrity in policy-making

This is one of my (thankfully, for some) rare forays into political issues on this blog. If you're a practicing scientist, engineer, or just a concerned citizen, please go here, read the statement, and sign the petition if you think it's an important issue. I know not everyone agrees with the Union of Concerned Scientists on every issue, but I think they're right about this one: science should speak for itself in policy-making, not be censored, manipulated, or heavily edited for political ends, by either party.

New Scientist: WTF?

Sci-Fi author Greg Egan, via John Baez: Save the New Scientist. Basically the British magazine New Scientist used to be very good - like Scientific American before they started cutting content for the sake of flashier visuals (basically trying to look more like Discover, though to be fair, Scientific American still has scientists do the actual writing, which is very nice). Over time, it's devolved to the point of being a conduit for press releases from the worst of the hype-spewers. The coup de grace that pushed Egan to write his plea was this COVER article, which conveniently neglects to point out that the gizmo in question would have to violate conservation of momentum if it works as described. Sad. A "science" magazine publishing, as a cover story, non-peer-reviewed junk that doesn't pass the laugh test.
(Not too much on cond-mat this week that seems good for the general blog reader - I'm sure more will come up soon.)

This week in cond-mat

Two papers from the past week, the first of which gives us a chance to discuss one of the on-going controversies in condensed matter physics.
cond-mat/0609301 - Lai et al., Linear temperature dependence of conductivity in Si two-dimensional electrons near the apparent metal-to-insulator transition
For years now, there has been a fairly heated debate about the nature of an apparent metal-insulator transition (as a function of carrier density) seen in various 2d electronic and hole systems. The basic observation, originally made in some Si MOSFETs of impressively high interface quality made in Russia, is that as the 2d carrier density is reduced, the temperature dependence of the sheet resistance changes qualitatively, from a metallic dependence (lower T = lower resistance) at high carrier concentration to an insulating dependence (lower T = higher resistance) at low concentration, with a separatrix in between with nearly T-independent resistance at some critical carrier density. A famous 1979 paper by the "Gang of Four" (Anderson, Abrahams, Licciardello, and Ramakrishnan) on the scaling theory of localization had previously argued that 2d systems of noninteracting carriers all become insulating at T=0 for arbitrarily weak disorder. So, the question is whether the real (interacting) case, with an apparent transition between metallic and insulating states, is profound (that is, a real quantum phase transition) or not (e.g., a percolative transition caused by the system breaking up into disconnected puddles of carriers as the concentration is lowered). There are some interesting pieces of evidence pointing in each direction. This paper weighs in using very nice Si quantum wells in SiGe, showing evidence consistent with a percolative crossover in the conductivity. Anyone out there care to comment on the state of this debate in general? Has there been a really slam dunk experiment out there that I've missed by avoiding this problem?

cond-mat/0609297 - Naik et al., Cooling a nanomechanical resonator with quantum back-action (also available in Nature)
This paper is one I need to read more carefully. These folks have constructed a nanomechanical resonator (operates at about 20 MHz), and are using a superconducting single-electron transistor (SSET) measured at high frequency to detect the resonator's motion. This is a great system for testing ideas about quantum measurement and back-action of the detector on the system being measured. In this case, they find that for the right settings of the SSET detector, they can actually cool the resonator (as determined by the noise temperature of the resonator, inferred from the readout of the detector) using the detector. The claim is that this is analogous to laser cooling in some sense, bit without a closer reading, I don't see how this really works. This shows that I need to think more and read more about this detector back-action business.

Packard Fellows meeting

Sorry for the downtime; the semester has begun, and this past week I also went to the annual meeting of Packard Fellows, which is a wonderful chance to hear technical talks from people working in all sorts of fields of the natural sciences, engineering, and mathematics. I will return with more cond-mat article discussions soon. In the mean time, I wanted to highlight two particular condensed matter talks that I heard at the meeting:

First, Hongkun Park spoke about his recent very interesting work on electronic properties of VO2 nanowires (actually bars - they grow from the vapor phase into long wires with square cross-sections). Some of this has been published. Vanadium dioxide is a weird material. It's supposed to be a Mott insulator at low temperatures, meaning that electronic interactions are so strong that the charges lock into place rather than being free to move around. At higher (not much higher than room) temperature, the material undergoes a first-order structural and electronic phase transition to a metallic state. Prof. Park's group has been playing with these nanowires, and found some amazing phenomena. For example, when the wires are sitting on a surface, the constraint of the surface strain plus the structural phase transition lead to the wires breaking up spontaneously into domains of metallic and insulating regions, and those domains can be (a) imaged with an optical microscope, (b) pushed around by flowing a current, and (c) made to oscillate back and forth because of resistive heating effects. Also, in suspended wires, the metal/insulator phase transition can be incredibly sharp, leading to the possibility of novel temperature sensors. Very neat.
Update: (9/27/06) This has just appeared in Nano Letters.

Second, Kathryn Moler showed her latest work on scanning SQUID microscopy. Basically it's possible to put an incredibly sensitive magnetometer at the very tip of an AFM-like probe, and image magnetic flux with incredible sensitivity. Most recently her group has been looking at superconducting fluctuations in little superconducting ring structures. Imagine putting a small magnetic flux on a superconducting ring. The fact that the superconducting wavefunction has to be single-valued going around the loop implies that magnetic flux through the loop is quantized. That quantization condition is enforced by spontaneous supercurrents in the loop. Well, for narrow loops its possible to be in a regime where rather than set up those currents, it's more energetically favored for the loop to go "normal". This is the Little-Parks effect. Now, if you imagine a split ring that looks just like the loop but isn't a complete circle, that would be superconducting. Can the topology of the ring really deeply affect the microscopic physics in the superconductor? Superconducting fluctuations in the "normal" ring are part of the answer. Again, a neat technique and a very nice piece of physics.

...and still MORE hype....

I have avoided talking too much about my own research here, with the intent of maintaining a broader perspective on CM and nanoscale physics. However, an example of nano-hype directly related to my own research has come up that I can't just let go (thanks to one of my regular anonymous contributors for pointing out the media aspects of this). Here is a perfectly reasonable theory paper about trying to make single-molecule transistors that operate in a new way. Basically the idea is to somehow (this trivial detail is left as an exercise for the experimentalists, which is actually fine for a theory paper like this) wire up three leads directly to a single small molecule. By varying the voltage on the "gate" lead, the quantum mechanical amplitude for tunneling from the source lead to the drain lead is modulated due to quantum interference. One could imagine (though this isn't discussed in the paper) implementing something like this in a GaAs quantum dot. For example, one could have a little "stub" dot off to the side of a channel connecting the source and drain. If the stub dot was tuned into the Kondo regime via coupling to the channel, then there would be a Fano antiresonance that would suppress source-drain conduction. Same basic idea. Anyway, the concept is sound, and the calculations (though done in some limited approximation on an idealized molecular/lead geometry) show that it's not crazy. Fine.

I have no problem with the science (though experimentally implementing it as conceived will be incredibly difficult). What I do have a problem with is the ensuing media onslought. Read this press release, which got picked up by CNN (broadcast, not the web). Read it all the way through, to the point where the scientist starts talking (I'm not making this up) about little nanobots controlled by computers that use this transistor concept swimming through your bloodstream. AAAAAGGGH! WHY DO PEOPLE DO THIS? Does the Arizona group really think that their paper will have more impact and enable more and better science and technology because of this? Do they think their pending patent on this idea will be more likely to be licensed? Don't they think that this kind of overreaching hype actually hurts the field in the long run?