PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 814 March 9, 2007 by Phillip F. Schewe, Ben Stein www.aip.org/pnu
*THE WOODSTOCK OF PHYSICS,* the famous session at the March 1987 meeting of the American Physical Society, earned its nickname because of the rock-concert fervor inspired by the convergence of dozens of reports all bearing on copper-oxide superconductors. The 20th anniversary of this singular event was celebrated this week at the APS meeting in Denver. Why such an uproar over the electrical properties of an unlikely ceramic material? Because prior to 1987 the highest temperature at which superconductivity had been observed was around 23 K. And suddenly a whole new set of compounds-not metallic alloys but crystals whose structure put them within a class of minerals known as perovskites---with superconducting transition temperatures above 35 K and eventually 100 K generated an explosion of interest among physicists. Because of the technological benefits possibly provided by high-temperature superconductivity (HTSC)---things like bulk power storage and magnetically levitated trains---the public was intrigued too. This week*s commemoration of the Woodstock moment (the months of feverish work leading up to the 1987 meeting) provided an excellent history lesson on how adventurous science is conducted. Georg Bednorz (IBM-Zurich), who with Alex Mueller made the initial HTSC discovery, recounted a story of frustration and exhilaration, including working for years without seeing clear evidence for superconductivity; having to use borrowed equipment after hours; overcoming skepticism from IBM colleagues and others who greatly doubted that the cuprates could support supercurrents, much less at unprecedented temperatures; and finally arriving at the definitive result-superconductivity at 35 K in a La-Ba-Cu-O compound. In October 1986 Bednorz and Mueller prepared a journal article confirming their initial finding in the form of observing the telltale expulsion of magnetism (the Meissner effect) from the material during the transition to superconductivity. Submitting this paper, however, required the approval of the IBM physics department chairman, Heinrich Rohrer who, that very week, had been declared a co-winner of the Nobel prize for his invention of the scanning tunneling microscope (STM). Afraid that he would not be able to obtain the preoccupied Rohrer*s attention, Bednorz obtained the needed signature by thrusting the approval form at Rohrer as if he (Bednorz) desired only a celebratory autograph. A scant year later Bednorz and Mueller pocketed their own Nobel Prize. The IBM finding was soon seconded by work in Japan and at the University of Houston, where Paul Chu, testing a YBaCuO compound, was the first to push superconductivity above the temperature of liquid nitrogen, 77 K. Very quickly a gold rush began, with dozens of condensed matter labs around the world dropping what they were doing in order to irradiate, heat, chill, squeeze, and magnetize the new material. They tweaked the ingredients list, hoping to devise a sample superconducted at still higher temperatures or with a greater capacity for carrying currents. At this week*s APS meeting Chu said that he and his colleagues went for months on three hours* sleep per night. Several other speakers at the 2007 session spoke of the excitement of those few months in 1987 when-according to such researchers as Marvin Cohen (UC Berkeley) and Douglas Scalapino (UC Santa Barbara)-the achievement of room-temperature superconductivity did not seem inconceivable. The Woodstock event, featuring 50 s peakers delivering their fresh results at a very crowded room at the New York Hilton Hotel until 3:15 am, was a culmination. In following years, HTSC progress continued on a number of fronts, but expectations gradually became more pragmatic. Paul Chu*s YBaCuO compound, under high-pressure conditions, still holds the transition temperature record at 164 K. Making lab samples had been easy compared to making usable power-bearing wires in long spools, partly because of the brittle nature of the ceramic compounds and partly because of the tendency for potentially superconductivity-quenching magnetic vortices to form in the material. Paul Grant, in 1987 a scientist at IBM-Almaden, pointed out that HTSC applications have largely not materialized. No companies are making a profit from selling HTSC products. Operating under the principle of *You get what you need,* Grant said, superconducting devices operating at liquid-nitrogen temperatures weren*t better enough so as to displace devices operating at liquid-helium temperatures. Nevertheless, the mood of the 2007 session (Woodstock20) was upbeat. Bednorz said the 1986/87 work showed that a huge leap forward could still take place in a mature research field whose origins dated back some 70 years. Bednorz felt that another wave of innovation could occur. Paul Chu ventured to predict that within ten years, HTSC products would have an impact in the power industry. Paul Grant referred to the study of superconductivity as the *cosmology of condensed matter physics,* meaning that even after decades of scrutiny there was still much more to learn about these materials in which quantum effects, manifested over macroscopic distances, conspire to make electrical resistance vanish, a phenomenon which at some basic level might also be related to the behavior of protons inside an atomic nucleus and the cores of distant neutron stars. (Photographs and an original summary press release from the 1987 meeting is available at our Physics News Graphics website, www.aip.org/png) HYPERACTIVE ANTIFREEZE PROTEINS, naturally secreted by an insect known as the spruce budworm, prevent it from freezing to death during winters in North American forests. Ohio University's Ido Braslavsky ([EMAIL PROTECTED]) and his colleagues presented studies of these potent yet nontoxic proteins at this week*s APS Meeting. Found in several other species such as snow fleas, the hyperactive proteins bind to ice, modify its crystalline shape, and prevent ice from growing further, effectively reducing the freezing point of ice for an organism that excretes them. These nontoxic substances have more recently been renamed "ice structuring proteins" (ISPs) to distinguish them from the toxic antifreeze products for automobiles. Extracting ISPs from biological sources has many potential applications, such as preserving organs and blood products, protecting against agricultural frost damage, and even preventing frostbite. These natural proteins are currently used in some "light" ice cream products to improve their texture, but those ISPs, derived from fish, are much less potent. How the hyperactive versions inhibit ice from growing is a topic of interest to Braslavsky's group and their collaborators, such as Peter Davies from Queen's University ([EMAIL PROTECTED]). The researchers attached fluorescent molecules, derived from jellyfish, to the protein. Through a microscope, they watched how the fluorescing ISPs inhibited ice crystals from growing. They observed that the ISPs prevent ice crystals from expanding in their normal disk-shaped form. Instead, they inhibit ice growth in certain directions and cause the crystals to grow in altered shapes. While a fish ISP promotes the growth of a "bipyramidal" ice-crystal form that looks like two pyramids whose bases are attached to each other, the spruce budworm ISP blocks growth in the preferred direction of the pyramid's apexes. Using the fluorescence microscopy they watched the proteins att ached to the ice blocking growth in this direction. (Meeting Paper J35.8, http://meetings.aps.org/Meeting/MAR07/Event/58982; for more information, see http://www.phy.ohiou.edu/~braslavs/APS2007/) *********** PHYSICS NEWS UPDATE is a digest of physics news items arising from physics meetings, physics journals, newspapers and magazines, and other news sources. It is provided free of charge as a way of broadly disseminating information about physics and physicists. For that reason, you are free to post it, if you like, where others can read it, providing only that you credit AIP. Physics News Update appears approximately once a week. 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