A Forum of The American Physical Society
Volume X No 3 Fall 2007
HISTORY OF PHYSICS NEWSLETTER
Reports from the March APS Meeting
Denver, CO, 5-9 March 2007
The 20th Anniversary of High-Tc Superconductivity: "Woodstock of Physics" Revisited
By Bill Evenson
On Monday, March 5, the Forum sponsored a symposium commemorating the 20th anniversary of the “Woodstock of Physics” session at the March 1987 APS meeting, where early work was announced on high-Tc superconductivity. It was an exciting and wonderfully successful session, with over a thousand people in attendance. Organized by Bill Evenson and Paul Grant, the session was chaired by Brian Maple, one of the original meeting chairs.
This anniversary session had eleven 15-minute talks, more like the original “Woodstock” than a regular APS invited session. The March 1987 affair was a post-deadline session with about fifty speakers, most of whom were allowed only seven minutes. It was held in New York City, and about two thousand physicists packed the room and overflowed into the hallway until after 3 a.m., when the session finally ended. The speakers this year were either participants in the 1987 session or deeply involved in those early days, and many others present in 1987 were in the audience for this anniversary. Speakers reminisced about that exciting time 20 years ago and commented on progress since then. To set the stage, Chair Brian Maple (University of California, San Diego) gave an “Introduction and Overview of the 1987 ‘Woodstock’ Session.” He showed slides of press clippings and gave a sense of the broad interest and excitement at that meeting.
Georg Bednorz (IBM Research, Zurich Research Laboratory), one of the original discoverers of high-Tc superconductivity who shared the Nobel Prize for this discovery with Alex Müller, talked about “The Discovery of High-Tc Superconductivity and the Countdown to the Rally.” He briefly addressed the guiding ideas on the road toward high-Tc superconductivity and the early work at the IBM Zurich Research Laboratory. He spoke about the environment and the decisive circumstances that in January 1986 led to the breakthrough with the discovery of superconductivity in cuprates. The pre-“Woodstock” period, which lasted less than a year, covers the time in which the Zurich team tested different La2CuO4-based compounds, confirmed the Meissner effect, and studied flux-trapping in these new materials. As news of the discovery started to spread during this period, the IBM/Zurich group experienced mixed reactions, ranging from silent skepticism to polite but cautious congratulations. This changed dramatically into excitement with the confirmation of the IBM/Zurich results by the Tokyo and Houston groups led by Tanaka and Chu, and culminated in the launching of the new field at the famous March 1987 meeting after the discovery of the 90 K superconductor. After that, it was “off to the races!”
C. W. “Paul” Chu (University of Houston, Hong Kong University of Science and Technology and Lawrence Berkeley National Laboratory) spoke about “High Tc: The Discovery of RBCO.” (RBCO stands for R = rare earth, B = barium, C = copper and O = oxide.) In his abstract, Chu wrote: “It was said by Emerson that ‘there is no history; there is only biography.’ This is especially true when the events are recounted by a person who himself has been heavily involved, and the line between history and autobiography can become blurred. However, it is reasonable to say that discovery itself is not a series of accidents but an inevitable product of each development stage of scientific knowledge, as was also pointed out by Holton.” The discovery of RBCO high-Tc superconductors was no exception. In his presentation, Chu briefly recounted several events that were crucial to the discovery: those occurring before 1986 that sowed the seeds for the group’s later high-temperature superconductivity research; those in 1986 that were critical to its discovery of the 93 K RBCO soon after Bednorz and Müller’s discovery of the 35 K high-Tc superconductor; and those that came in 1987 after the barrier of the 77 K boiling temperature of liquid nitrogen was finally overcome.
Douglas J. Scalapino (University of California, Santa Barbara) described “Some Prehistory to Woodstock” in relating the story of two talks that provided a preview of the excitement that was to spill over at the 1987 gathering. The first was an unscheduled talk on LaBaCuO by Prof. K. Kitazawa on 5 December 1986 at a Materials Research Society symposium on superconducting materials held in Boston. The second was a quasi-public disclosure by Chu at UC Santa Barbara in late February 1987 regarding his work on superconductivity above 77 K.
The next seven talks described high-Tc activities that immediately followed the announcement of the discovery by Bednorz and Müller: “The 1987 High-Tc ‘Woodstock’ Session and High Tc at IBM,” by Paul M. Grant (IBM Research Staff Member, Emeritus); “Bell Labs and High Tc,” by Robert J. Cava (Princeton); “High Tc and Condensed Matter Theory in 1987,” by Marvin L. Cohen (University of California, Berkeley); “Early High-Tc Activity in Japan: The Franco Rasetti Lecture,” by Shoji Tanaka (Superconductivity Research Laboratory/ISTEC, Tokyo, Japan); “High Tc at BellCore,” by Laura H. Greene (University of Illinois at Urbana-Champaign); “High Tc at Stanford,” by Aharon Kapitulnik; and “High-Tc Superconductivity—1987,” by Douglas Finnemore (Iowa State University). Space does not permit full discussion of these talks, but the early work of the Tanaka group in Japan warrants additional comment. (Note that Tanaka gave the Franco Rasetti Lecture, funded in honor of Franco Rasetti through a much-appreciated donation from Robert Resnick).
Tanaka writes: “From 1960 to 1980, R&D on superconductivity in Japan was carried out mainly to improve A15 superconducting wires and magnets. Improvements of wires were made mainly in the National Institute for Metals, and improvements of superconducting magnets were made in the Japan Atomic Energy Research Institute for future nuclear-fusion reactors, the National Railway Laboratory for future maglev trains and also in the Electro-Technical Laboratory for magneto-hydrodynamical generators. I began the study of BPBO (BaPb1-xBixO3) in 1975 and at that time the research on oxide superconductors was limited to my laboratory in the University of Tokyo. During the study of this new superconductor, we learned quite a lot on how to make ceramic samples as well as how to measure electrical conductivity and magnetic susceptibility at low temperatures. In 1982, Prof. S. Nakajima organized a rather small group for investigating ‘New Superconducting Phenomena,’ and I became a member of the group. In 1985, Nakajima expanded the research group to include more than five experimentalists and five theoreticians. The research was on new superconducting materials, with funding from the Ministry of Education of Japan. In late October 1986, we followed the first paper of Bednorz and Müller, and immediately obtained high-temperature superconductivity and reported it at a group meeting in early November. In early December, we confirmed that La2-xBaxCuO4 was a true high-temperature superconductor, with a critical temperature of 28 K. Asahi Shimbun, Japan’s largest newspaper, announced this result in its science section, and many people knew that high-temperature superconductivity had been discovered. Then many physicists and chemists rushed to this field, and many new kinds of materials were soon synthesized. The Ministry of Education, the Ministry of International Trade and Industry, and the Agency for Science and Technology began to make new development plans of their own. Superconductivity fever had reached Japan.”
Many, many laboratories around the world made important contributions to the science of high-Tc superconductivity. Although only a small sample of the many early researchers, the speakers in this session were able to recall some of the excitement of the 1987 “Woodstock of Physics” gathering. As Doug Finnemore, wrote, “The discovery of superconductivity in the cuprate class of conducting oxides brought a flash of sunlight onto one of the fields of condensed-matter physics that many of us had thought was rather mature and fairly well understood. In addition to opening a whole new class of materials to the study of correlated motion of charge carriers, it opened a new mind-set that materials with complex chemical bonding can lead to totally new phenomena. The tasks of materials preparation escalated, and with it came the development of totally new spectral probes of the electron gas and the electronic structure in metals.”
That same Monday, March 5, the Division of Condensed Matter Physics held a special evening session on “50 Years of BCS Theory,” celebrating the 1957 publication of “Microscopic Theory of Superconductivity” (Phys. Rev. 106, 162) by John Bardeen, Leon N. Cooper and J. Robert Schrieffer. Several hundred attended the session, which was chaired by Charles Slichter. It featured three speakers: Douglas J. Scalapino (University of California, Santa Barbara) on “The Impact of the BCS Theory on Condensed Matter Physics”; John M. Rowell (Arizona State University) on “The Impact of the BCS Theory on 50 years of Superconductivity and Condensed Matter Physics”; and Gordon Baym (University of Illinois at Urbana-Champaign) on “BCS—from Atoms and Nuclei to the Cosmos.” They discussed the profound influence of BCS theory throughout our field, from condensed-matter physics to elementary-particle theory and cosmology.
Condensed Matter Physics at Synchrotron Facilities: History as Prologue to the Future
By Bill Evenson
On Wednesday, 7 March 2007, the Forum and the Division of Physics of Beams jointly sponsored a symposium on Condensed Matter Physics at Synchrotron Facilities. It was organized by Catherine Westfall, who enlisted the help of Denis McWhan and David Moncton—who chaired the session. About a hundred persons attended.
The session led off with Joachim Stöhr of the Stanford Synchrotron Radiation Laboratory speaking on “Soft X-Ray Science: From Photon Drought to X-Ray Lasers.” He defined soft X-rays as 0.2–2.0 keV photons, with wavelengths of about 1–10 nm—which require the use of grazing-incidence optics. Stöhr described the major technical developments, beginning in about 1975, that made high-intensity soft X-rays available, today with meV spectral resolution, picosecond pulse lengths and nanoscale spot sizes. He pointed out why soft X-rays are so useful: large X-ray absorption cross sections; narrow lifetime widths; important absorption edges of elements in the spectral range; large resonance and polarization effects; and nanometer-scale wavelengths that allow nanoscale imaging. Their tunable energy and polarization permit control of electronic core-to-valence transitions that provide access to the fundamental charge and spin properties of valence electrons in matter. The large cross sections associated with absorption-edge resonances provide sensitivity to small numbers of atoms, as are encountered in nanostructures, ultra-thin films, interfacial layers and surfaces. Presently, the most advanced experiments use sophisticated spectro-microscopy and lens-less coherent imaging techniques with nanoscale spatial and picosecond temporal resolution. In summary, soft X-rays offer capabilities complementary to hard X-rays; spectroscopic studies reveal atom-projected charge and spin properties of valence electrons; microscopic studies reveal charge and spin distributions at the nanoscale; and time-dependent studies examine nanoscale dynamics at intervals down to tens of picoseconds. On the horizon are experiments with soft X-ray lasers which, among other things, will provide femtosecond snapshots of matter.
John Hill of Brookhaven National Laboratory spoke next on “Inelastic X-ray Scattering.” The technique of inelastic X-ray scattering probes the dynamics of a system—its atomic and molecular excitations. Hill gave a broad overview of the field, its history, some recent experiments, and a brief look at the future. Inelastic X-ray scattering experiments may be divided into roughly two classes; those performed with meV energy resolution, which observe phonons and other collective ionic motions, and those performed with eV resolution, which look at electronic excitations. The first phonon experiments were done 20 years ago, and two recent examples were presented, one a study of liquid Al2O3 and the other observing the surface of liquid indium. The first electronic measurements were performed 40 years ago, and two recent examples were presented, one a study of excitons in organic semiconductors, and the other of mid-infrared excitations in cuprates. Inelastic X-ray scattering as a complement to neutron scattering has been suggested for many years, with first attempts dating back to the 1980s. The advent of hard X-ray third-generation synchrotron light sources has allowed its establishment as a routine, powerful technique for condensed-matter studies. It has enabled important breakthroughs in our understanding of phonon-like excitations in disordered materials and matter under extreme conditions. In looking to the future, Hill noted some recent developments at existing sources and pointed to proposed new X-ray sources, such as the NSLS-II project, which would lead to large gains for inelastic X-ray scattering.
The third talk was on “Surface Structure as a Foundation of Nanotechnology,” by Ian Robinson of the London Centre for Nanotechnology and Diamond Light Source. The three generations of synchrotron sources achieved to date—parasitic, dedicated and undulator-based—have each revolutionized research in X-ray diffraction. Surface-structure measurements, demonstrated already with Coolidge-tube sources, benefited from the enormous flux gain of the first generation. Dedicated second-generation light sources such as NSLS allowed in-situ surface preparation and reliable, steady beams to be available when a surface was ready to measure. Third-generation sources, such as the Advanced Photon Source, had enormously improved brightness and coherence, and thus allowed access to the surfaces of nanoparticles. Robinson illustrated how these technological advances led to two significant scientific breakthroughs. The concept of crystal-truncation rods led to new views of how the surface is a modification yet still an extension of the bulk crystal structure. And the development of lens-less coherent X-ray diffraction imaging has allowed access to the structure of nanocrystalline materials by three-dimensional phase mapping of the particle interiors. The structural principles of these new nanomaterials are now being investigated using these new methods.
Next, Denis McWhan of MIT spoke about “Magnetic X-Ray Scattering.” He compared magnetic scattering during the period 1965–1981, before synchrotron sources became widely available, and in 1985–1992. During the 1980s, three factors converged: the development of synchrotron sources; the development of techniques to grow new materials layer by layer; and the realization that X-rays could probe the magnetic properties of materials. In addition to magnetic X-ray scattering, most magneto-optical effects have been extended from the visible to the soft X-ray region. Because both beam energy and polarization are tunable, synchrotron sources are element- and site-specific probes—and there are large resonant enhancements in the scattering or absorption cross sections at atomic absorption edges. Synchrotron radiation is routinely used to study the magnetic polarization of different components of a material and to separate their spin and orbital angular momentum densities. It allows one to probe magnetic polarization level-by-level (p, d, or f) and component-by-component using resonant scattering. It has also been used to determine the magnetic polarization at interfaces and surfaces and magnetism in extreme environments using small samples. In addition, synchrotron radiation can be used to determine the interplay between the atomic, orbital and magnetic ordering in materials. Future possibilities include further development of the spectroscopic aspects of magnetic scattering and probing magnetism on smaller length scales and at shorter time intervals.
The final talk was on “The Use of Coherent X-Ray Beams to Study the Dynamics of Soft Condensed-Matter Systems” by Sunil Sinha of the University of California, San Diego. One of the most powerful techniques for studying dynamics in soft condensed-matter systems has been dynamical light scattering. Over twenty years ago, it was recognized that a similar application of X-rays (in order to achieve shorter length scales and avoid problems of multiple and stray particle scattering) could open up whole new areas of research. But the potential of coherent X-rays was not anticipated when high-brightness third-generation synchrotron radiation sources were planned! Nevertheless, their usefulness in this field has been enormous, making it possible to deliver intense beams of highly coherent X-rays and enable many new applications of X-ray scattering. In particular, the technique of X-ray photon correlation spectroscopy (XPCS), the X-ray analog of dynamical light scattering, has now become an exciting new research area with primary applications in soft condensed matter. The first observation of speckle by diffraction of coherent X-rays was reported in 1991, and a rapid expansion of this field followed. Current applications include studies of dynamical fluctuations in colloids and polymers and of surface fluctuations in liquid films and membranes. XPCS has yielded interesting new results on these systems, which are difficult if not impossible to obtain by other techniques. In the future, physicists anticipate XPCS with completely coherent beams and time resolutions down to nanoseconds.
March Contributed-Paper Session I
By Bill Evenson
On Tuesday afternoon, March 6, the Forum held the first of two contributed-paper sessions at the APS Meeting in Denver. Chaired by Bill Evenson, it included six history talks witnessed by an audience of about 50.
Jean-François Van Huele of Brigham Young University led off with an interesting talk entitled, “The Missing Part in the Story of Spin: What is the Spin Content of Stern-Gerlach?” During the development of the idea of spin in quantum mechanics, after the Stern-Gerlach effect was known, this effect did not seem to influence the conception or acceptance of this idea, he explained. Although the experiment is widely interpreted today as a manifestation of spin, it was not seen that way initially and did not influence the development of the quantum-mechanical concept of spin. Van Huele examined the connection between spin and the Stern-Gerlach effect and reviewed the lack of mutual influence in the publication record, giving possible historical reasons for the absence then of what seems an obvious connection today.
Supported by a Bardeen Studentship, Cesar Rodriguez of the University of Texas, Austin, spoke on “The Entangled Histories of Physics and Computation.” He focused on how the histories of physics and computation intertwine in a way relevant to quantum computation. Leibniz not only pioneered calculus but also left his footprint in physics and invented the concept of a universal computational language. This idea was further developed by Boole, Russell, Hilbert and Gödel. Boltzmann and Maxwell established the foundations of information theory, as later developed more fully by Shannon. Partly stimulated by World War II, von Neumann and Turing also played important roles in the field. Recently, new cryptographic developments have led to a reexamination of the fundamentals of quantum mechanics, and quantum computation is discovering a new perspective on the nature of information itself.
“Einstein’s Jury: Trial by Telescope” was the topic of a talk by Jeffrey Crelinsten, author of the recent book, Einstein’s Jury: The Race to Test Relativity (Princeton University Press, 2006). He addressed the process of acceptance of special and general relativity. Relativity was poorly understood between 1905 and 1930, and Einstein worked hard to make it more accessible to scientists and scientifically literate laypeople. Its acceptance was largely due to the astronomy community, which undertook precise measurements to test Einstein’s astronomical predictions. The well-known 1919 eclipse measurements that made Einstein famous still did not convince most scientists to accept relativity, said Crelinsten. The 1920s saw numerous attempts to measure the gravitational bending of light, as well as solar line displacements and even an aether drift. He discussed how astronomers approached the “Einstein problem” in these early years before and after World War I, and how the public reacted to what they reported, as well as how this work helped to shape attitudes we hold today about Einstein and his ideas.
“Forty Lost Years of Coherent States” was the topic addressed by Kavan Modi University of Texas, Austin, recipient of a Bardeen Studentship. He pointed out that Schrödinger introduced the minimum-uncertainty state in 1926 in his effort to satisfy the correspondence principle. But it was almost forty years later, in 1963, that Glauber put these states to use in what is now known as the quantum theory of optics, giving them the name used today, “coherent states.” Soon thereafter, Sudarshan completed Glauber’s unfinished work in achieving the full theory of quantum optics. Crucial mathematical work had been done in the intervening years so Glauber could make use of these states. Modi discussed what Schrödinger had been trying to do, why Glauber was attracted to these states, and why they were forgotten for almost forty years.
Norman Redington spoke on “The Reception of the Kaluza Theory in Britain, 1921–1958.” Kaluza’s five-dimensional unified theory was part of a wider program to geometrize physics that was largely abandoned in the wake of the mid-1920s successes of quantum mechanics. However, a small group of British physicists continued to work on the subject through the middle decades of the 20th century. Redington reviewed their efforts and the reception of these ideas by the physics community.
The final talk was “On the Origins of the Raman Effect” by Somaditya Banerjee of the University of Minnesota, recipient of a Bardeen Studentship. He reviewed the events that led to the discovery of the Raman effect by C. V. Raman and K. S. Krishnan at Calcutta in 1928. He presented evidence that although the effect was generally seen as providing strong evidence for the quantum nature of light, Raman himself was a staunch supporter of the classical wave theory of light. Banerjee placed this historical analysis in the context of a larger project seeking to understand the role of Raman scattering in the experimental verification of the quantum dispersion theory of Hendrik A. Kramers, which formed a conceptual bridge between Bohr and Sommerfeld’s “old” quantum theory and Heisenberg’s matrix mechanics.
March Contributed-Paper Session II
By Catherine Westfall
The contributed-paper session held by the Forum on Thursday morning, March 8, included four history papers, summarized below, and three others. About 25 people attended the session. The papers were interesting and the audience receptive, which made for a friendly and lively session.
The session began with a paper by Willem van de Merwe and Todd Ream (Indiana Wesleyan University) titled “Compartmentalization of Science, Power, and Social Responsibility as Exemplified in the Life of J. Robert Oppenheimer.” Using recent biographies of Oppenheimer as a starting point, the presentation centered on his pre-Los Alamos years, noting his attendance as a child at the Ethical Cultural School in New York City, his studies as a physics graduate student in Europe, his sympathy with left-wing politics as a young professor, and his passion for poetry—including the Bhagavad-Gita—that endured throughout his life. Using Oppenheimer as an example, the authors concluded that having a high-quality liberal arts education can help physics students formulate a framework for a more meaningful career in science.
The next paper, “The English Revision of The Blegdamsvej Faust,” by Karen Keck (Net Advance of Physics), added a different twist to the blending of science and the liberal arts. She addressed the updated version of Goethe’s Faust presented at the 1932 meeting of quantum physicists at Niels Bohr’s Copenhagen Institute. As Keck pointed out, the most widely read version of the play, which features Wolfgang Pauli tempting Paul Ehrenfest to accept a chargeless, massless particle, was an English translation of the German original provided by George Gamov’s second wife for his book Thirty Years that Shook Physics. Although this portrayal of the play is well known, Keck provided a fascinating analysis of how Barbara Gamov rearranged and added to the parody to strength the similarities between it and Goethe’s original and to reflect her husband’s views, particularly on the international and cooperative aspects of physics.
The third paper in the session, “An 18th Century Thermometer Recipe,” took us back in time and to another venue. Presenter Durruty Jesús de Alba Martinez (University of Guadalajara) told the story of a manuscript containing instructions on how to build a thermometer that was found in the Special Funds Collection of the Jalisco’s State Public Library and attributed to Francisco Javier Clavigero (1731–1787). He was an important early educator at a the Colegio de Santo Tomàs, a Jesuit institution that provided college-level education before the opening of the University of Guadalajara. This manuscript is intriguing because it was inserted into a vellum-bound volume and is in Spanish, not Latin as in the rest of the volume. The paper explained how the instructions were actually used to construct the thermometer and speculated about how the manuscript could have been used as the experimental part of a physics course.
The session ended with a paper that took the audience in yet another direction, “Historical Perspectives on Respiratory Fluid Dynamics and Flow Phenomena Deep in the Lung.” Authors Josue Sznitman (ETH Zurich) and Akira Tsuda (Harvard School of Public Health) gave a historical review of the 30-year-long study of respiratory fluid dynamics and flow phenomena deep in the lungs. The authors noted that after the first pioneering work on flow resistance in passageways, researchers conducted studies elucidating the nature of airflow in the upper (nose, larynx) and conducting passageways. At first, relatively little attention was given to the airflow in the deeper regions of the lung, characterized by 300 million pulmonary alveoli providing gas exchange with blood. For a long time the argument prevailed that airflow velocities in the alveolar region are negligible due to a large increase in the total cross-sectional area at that level; in fact, this view is still taught in medical schools. In the last 20 years, however, new theories have been developed to explain the experimental observation of convective mixing of inhaled particles deep in the lung. These theories suggest that convective airflow in the alveolar region is in fact relevant, and posit that alveolar flows are much more complex than previously thought, perhaps even exhibiting chaotic flow. The authors concluded that such discoveries constitute a small revolution in our understanding of respiratory flows deep in the lung.
