Wednesday, August 08, 2007

US Condensed-Matter Community Grapples With Availability of Crystalline Samples

This problem seems to be flying under the radar till recently, but the issue has been around for years and years. Only now is it getting to a worrying state.

In condensed matter physics, the one important aspect is the experimental study of various materials using a zoo of different methods. But the main ingredient remains the same - the availability of suitable and high-quality samples to study on. This is the only way discover can be made and theories can be tested. I have personally seen how the advancement of high-quality high-Tc superconductors have affected our ability to study it and understand the salient characteristics of this class of material. It allows us to separate out what features are truly intrinsic to the material, and what are the red herrings that are due to bad samples.

In this report, the shortage of skills, personnel, and availability of high-quality samples in the US is discussed and appears to be reaching a critical state.

The US "is a second-class, if not a third-class, citizen" in terms of investment in the synthesis of high-temperature superconductors, heavy-fermion materials, thin films, single crystals, ultrapure semiconductors, and other specialized samples for condensed-matter experiments, says Cornell University's Séamus Davis. US scientists "have to go cap in hand to the people who lead the development of new materials in these research fields." Davis gets samples for his spectroscopic imaging scanning tunneling microscopy (STM) studies from colleagues in Japan, Canada, and the UK. "From the pure perspective of science," he says, "things are great. It's from the parochial perspective of how much belongs to the US that you may think there is a problem."

If you look at many experimental papers related to this, you'll see many "collaborators" from Japan, China, etc., whose major involvement in those work was supplying high-quality samples that were used in the studies. There are just aren't that many in the US that are able to produce as much as wide a variety of these materials. Even when there is, many of these skilled personnel either are retiring, or have retired. Example: Dave Hinks at Argonne, who has produced some of the best quality Bi-2212 high-Tc superconductors. He has technically retired, but he still shows up at work often. The condensed matter group at Brookhaven, on the other hand, had a terrific foresight to correct a problem that they had for years. They didn't have anyone in-house to produce these high-quality high-Tc superconducting samples that they were studying until a few years ago when they managed to hired G.D. Gu and bought a floating-zone furnace to start producing these samples. This is such a smart move and now they no longer have to depend entirely on sources from various institutions.

So yes, I can certainly see this becoming a major problem here in the US. The only thing I don't understand is why did it get to this stage. Is it entirely due to the perceived low "prestige" or payoffs, as implied in the article? Many of these skilled people actually came out of chemistry or material science. Is there a lack of recruitment from that field of study?

I would also say that this problem isn't necessarily confined to just condensed matter. There is also a lack of expertise in producing an adequate supply of materials, especially photocathodes, in accelerator physics. For my part, I ended up designing and assemblying our own high quantum efficiency photocathode fabrication system for our accelerator. In other words, make one for our own use. It is convenient, and it is not dependent on the "kindness of others". Luckily, unlike the materials needed in condensed matter, the "quality" issue isn't as crucial in our case, and it isn't as big of a project to build our fabrication system for this purpose (it still took roughly 2 years of planning, assembling, and testing).

So the availability of the material is important. No material, no study!


No comments: