True Genius: The Life and Science of John Bardeen: The Only Winner of Two Nobel Prizes in Physics (2002)

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12 Two Nobels Are Better Than One Hole in One B ardeen gradually settled into the role of physics guru, the authority to consult on almost any problem. In both the physics and electrical engineering departments at the Univer- sity of Illinois, “John will know” became a familiar refrain. Bernard Serin, who spent the 1958–1959 academic year at Illinois as a visiting research associate professor, observed the flow of colleagues and students who passed through Bardeen’s office seeking advice. Serin later told a colleague it was like “sharing an office with Buddha.” Bardeen’s scientific court extended beyond the university and even beyond the physics community. His many invitations included a White House dinner in April 1962, at which forty-nine Nobel laureates dined with a distinguished group of additional guests, including the astronaut John Glenn, the poet Robert Frost, and the author John Dos Passos. President Kennedy entertained the group gathered in the State Dining Room and neighboring Blue Room with his famous extemporaneous remarks. “I think that this is the most extraordinary collection of talent, of human knowl- edge, that has ever been gathered together at the White House— with the possible exception of when Thomas Jefferson dined alone.” Jane wrote to her family, “We felt greatly honored to be there in the company of so many distinguished people.” In 1963 Bardeen’s office moved into a larger space that he would occupy for the next twenty-seven years, in a new building con- structed for the physics department several blocks east along Green 219 

220 TRUE GENIUS Street. The building would later be named the Loomis Laboratory of Physics in honor of Wheeler Loomis. The old physics lab, built in 1909, had provided ample work space in its first two decades. But by the 1940s the department was making use of all manner of additional space to accommodate its needs. Its cyclotron had to be housed in a garage. When, by the 1950s, “every nook from basement to attic” became fully occu- pied, a new building was planned. As the department initially could secure enough funds to construct only half of the new building, the eastern portion that was built first had exposed concrete blocks forming its western wall. These blocks became the walls of inte- rior rooms when it was possible to build the western half of the building between 1961 and 1963. In September 1963 the many-body group, including Bardeen, moved into a multi-office suite on the third floor of the new part of the building. Three of the suite’s four offices were lined up next to one another along the south wall. The fourth office faced west. Bardeen chose the first of the three south-wall offices. He lined several desks up along the east wall and organized his library on shelves above. Blackboards decorated the other wall. Two file cabinets stood near the window. Bardeen usually worked beside the window, through which he could see the afternoon sun brighten the trees near a residence hall. He usually left his office door open while working. Bardeen’s move created an unexpected problem for some of his colleagues. In the crowded old building, Bardeen had worked in a shared office. When a colleague came to ask him a question, it was not necessary for them to wait for Bardeen’s answer, which could take up to half an hour or more to arrive. Bardeen’s office mate could receive the answer and later deliver it to the questioner. In the new office this system didn’t work. The new arrangement did, however, promote collaboration within the many-body group. David Pines, in the office next to Bardeen’s, enjoyed frequent discussions with Bardeen over the years on a wide range of many-body problems, including quantum plas- mas, electrons in metals, collective excitations in solids, supercon- ductivity, nuclear structure, compact helium liquids, and high- temperature superconductivity. Pines had returned to Urbana in 1959 after four years at Princeton (as an assistant professor and then as a member of the Institute for Advanced Study). 

Two Nobels Are Better than One Hole in One 221 Two recently hired young theorists, Leo Kadanoff and Gordon Baym, moved into the suite’s remaining two offices. After complet- ing graduate study at Harvard, both had worked in Copenhagen during 1960 as postdoctoral associates at the Universitetets Institut for Teoretisk Fysik (now the Niels Bohr Institute). They had col- laborated on problems of transport in many-body systems using Green’s functions, including “gauge invariance” and other symme- tries. They also coauthored a research monograph on quantum sta- tistical mechanics. By the time Kadanoff and Baym accepted permanent positions at Illinois, in 1961 and 1962, respectively, they were already recognized as leaders in many-body theory. The de- partment had become one of the three most important centers for many-body physics, along with Bell Labs and the Landau Institute in Moscow. Bardeen, Pines, Baym, and Kadanoff worked in a loose collabo- ration, often wandering into one another’s offices to talk problems through. One memorable collaboration involved John Wheatley, an experimentalist who was studying the Fermi liquid properties of 3 He at low temperatures. When Bardeen learned that David Edwards of Ohio State had demonstrated that 3He can dissolve into superfluid 4He, he immediately recognized the opportunity to study a new Fermi liquid, one that he thought could become a superfluid. The three theorists, Bardeen, Baym and Pines, formed a col- laboration with the experimentalists, Wheatley and Edwards, one that also included Wheatley’s former graduate student, Andy Anderson, who was now a postdoc. Wheatley’s lab was just down- stairs in the physics building, and the three theorists regularly looked in on his experiments. Bardeen, Baym, and Pines developed a theory for the intriguing 3He–4He mixtures—intriguing because the particles of 3He are fermions (obeying Fermi-Dirac statistics), while those of 4He are bosons (obeying Bose-Einstein statistics). Although the 3He particles form a normal fluid, the calculations, drawing on a suggestion of Bardeen’s to use an “effective interac- tion” for describing the 3He, indicated that the 3He would become superfluid at very low temperatures (several millikelvin). The sys- tem would thus become a composite of two independent superflu- ids, each with different properties. (This phenomenon has not yet been observed experimentally in dilute solutions.) Once again, Bardeen served as the leader of the team, the one who knew what questions to ask. 

222 TRUE GENIUS The Illinois many-body group continued to grow around Bardeen. Christopher Pethick joined as a postdoc in 1966–1967. In early 1966 Michael Wortis, who specialized in magnetic systems and eventually phase transitions, came as a research assistant pro- fessor. In 1972 three new permanent members joined as assistant or full professors: Vijay Pandaripande, an expert in the nuclear many-body problem. Frederick Lamb, a student of astrophysics, and Bardeen’s former student Bill McMillan, who returned from Bell Labs, where he had gone after taking his degree in 1963. In 1982 Anthony Leggett, who had been a postdoc with the group in 1964– 1965 and again in 1967, joined permanently. Bardeen spent part of most days answering questions posed by his colleagues and students. Because of his detailed technical knowledge of physics, he could often point directly to the heart of a problem—and to its solution. But there were times when Bardeen’s colleagues could not grasp the master’s meaning. A few pressed for elucidation; many simply accepted his judgment—after all, he had been right countless times before. Colleagues and students were not the only ones to trust Bardeen’s intuition. He did so himself. Occasionally this habit led to embarrassment. In the realm of classical physics, particles cannot pass through concrete walls. But they can do so in the quantum-mechanical world if they try often enough. In fact, in this strange world, an electron or other elementary particle has a finite (if typically extremely small) probability of “tunneling” through a physical barrier. For the case of a supercurrent, however, it would appear that traversing a barrier between two superconducting materials would be too improbable to occur in nature, because a pair of elec- trons would have to pass through at the same time. In 1962 Brian Josephson, a 23-year-old graduate student of Brian Pippard, looked into this matter carefully. His theory predicted that electron pairs in superconductors should be able to tunnel through a thin barrier separating two superconductors. The phe- nomenon became known as the “Josephson effect.” Its existence became the subject of a famous debate between Bardeen and Josephson. The physicist Donald G. McDonald has studied this debate, staged in September 1962 at a major physics conference. McDonald interviewed many of those involved and reviewed docu- ments from the period. His work has informed our account. Bardeen became involved in the question of superconducting 

Two Nobels Are Better than One Hole in One 223 tunneling during the summer of 1960, while on a consulting visit to the General Electric Research Laboratory in Schenectady, New York. There he conferred with one of Seitz’s recently graduated Ph.D. students, Walter Harrison. They discussed experiments that Ivar Giaever had done while he was a graduate student at Rennselaer Polytechnic Institute. They revealed quantum-me- chanical tunneling of electrons from a normal material into a su- perconducting one. When Harrison pointed out that for certain systems Giaever’s assumptions would need modification, Bardeen said he was inter- ested in taking a closer look at the whole question of tunneling in superconductors. He checked with Harrison to make sure it was not “cutting in” on him. Harrison assured him it was not. That fall Bardeen developed a theory of superconducting tunneling based on the assumption that in the region of the barrier the electrons “are not paired and the wave function is essentially the same as in the normal state.” Bardeen’s paper on superconducting tunneling raised criticism from a theorist in the physics department at the University of Chicago, James C. Phillips, who felt that Bardeen’s argument was unclear. Phillips joined his colleagues Leo Falicov and Morrel Cohen in a discussion of the tunneling problem that resulted in February 1962 in a joint paper. Their work treated the case of tunneling through a barrier separating a superconductor and a normal metal. Five months later Bardeen responded to Phillips et al. in an- other paper on the same subject. This one included a footnote refer- ring to a recent publication by Josephson. Following up on his earlier assumption that in the region of the barrier the electrons are not paired, Bardeen intuitively judged Josephson’s suggestion “of superfluid flow across the tunneling region [between two super- conductors] in which no quasi-particles are created” as impossible. Bardeen stated that “pairing does not extend into the barrier, so that there can be no such superfluid flow.” Josephson was then at the end of his second year at the Royal Society’s Mond Laboratory in Cambridge. He had taken a course on many-body theory from Philip Anderson, who was also in Cam- bridge that year (1961–1962), on a sabbatical leave from Bell Labs. Anderson found teaching this course “a disconcerting experience, I can assure you.” For “everything had to be right or he [Josephson] 

224 TRUE GENIUS would come up and explain it to me after class.” As part of the course Anderson had introduced the concept of broken symmetry in superconductors. Josephson “was fascinated by the idea of broken symmetry, and wondered whether there could be any way of observing it experimentally.” After learning of Giaever’s tunneling experiments and having also studied recent experimental work by Hans Meissner and theo- retical work by Robert Parmenter, Josephson went to Pippard with his idea that supercurrent flow might indeed be possible. Pippard had himself thought it “perfectly possible for this superconductor to infect that normal metal with superconducting pairs so that supercurrent could pass from one side to the other.” But he had argued that the probability of two electrons tunneling simulta- neously through an insulating barrier of the kind Giaever had used would be so small as to be unobservable. Josephson was not so sure, especially when Anderson showed him a preprint of the Cohen, Falicov, and Phillips paper on the superconductor-barrier-normal metal system. He tried to extend the calculation to the situation where both sides of the barrier were superconductors and was surprised to find a term dependent on the phase. The current, an even function of the voltage, did not vanish when the voltage was zero. There did indeed appear to be a super- current, despite Pippard’s suspicion that pair tunneling would have too small a probability to be observable. Josephson discussed his puzzling finding with both Pippard and Anderson. “It was some days before I was able to convince myself that I had not made an error in the calculation,” Josephson said. “We were all—Josephson, Pippard and myself, as well as vari- ous other people who also habitually sat at the Mond tea and par- ticipated in the discussions of the next few weeks—very much puzzled by the meaning of the fact that the current depends on the phase,” Anderson wrote. “By this time I knew Josephson well enough that I would have accepted anything else he said on faith. However, he himself seemed dubious, so I spent an evening check- ing one of the terms that make up the current.” Together Anderson and Josephson “discussed how broken symmetry made this pecu- liar behavior of the current possible.” Josephson’s result stood fast. He was ready to publish. “The embarrassing feature” of the work was “that the effects predicted were too large,” Josephson later wrote in his Nobel 

Two Nobels Are Better than One Hole in One 225 address. Because of some uneasiness with the results, he submitted his paper on June 8, 1962, not to Physical Review Letters but to the new journal Physics Letters. He wrote that in a tunneling experiment when both metals are superconducting, “new effects are predicted, due to the possibility that electron pairs may tunnel through the barrier leaving the quasi-particle distribution unchanged.” This paper was received by Physics Letters on June 8, 1962. Two weeks later Bardeen submitted his paper to Physical Review Letters, with the footnote challenging Josephson’s theory. Bardeen’s challenge came to the attention of the organizing committee of the Eighth International Low Temperature Physics Conference (LT-8), held September 16–22, 1962, at Queen Mary’s College of London University. The organizers had “wanted macro- scopic quantum phenomena to be a major theme of the confer- ence.” The Harvard physicist Paul Martin was chair of a session that included, among other topics, tunneling. He invited Josephson and Bardeen to appear face to face in a public debate. At that point the effect predicted by Josephson and questioned by Bardeen had not yet been confirmed. The debate, although not mentioned anywhere in the confer- ence proceedings, was well attended. Bardeen, who had opened the conference with the Fritz London Memorial Lecture, met briefly with Josephson shortly before the debate. “I introduced Josephson to Bardeen in London, when people were milling around in a big hall,” Giaever recalled. When Josephson tried to explain his theory to Bardeen, “Bardeen shook his head slightly and said ‘I don’t think so,’ because he had carefully thought about the problem. I stood there during the short conversation. Then Bardeen left, and Josephson was quite upset.” They proceeded into the conference room, which “was crowded late in the afternoon, in anticipation of the debate,” wrote McDonald. Bardeen sat near the back. Josephson began with a brief outline of Anderson’s notion of broken symmetry in super- conductors. Drawing on Lev Gor’kov’s formulation of the BCS theory, he explained how his calculations “predicted that pair tunneling would be a large effect.” Then “Bardeen rose to describe his theory of single-particle tunneling including his previously published comment that pairing does not extend into the barrier.” Josephson interrupted with questions. Bardeen came back with answers, and with questions of his own for Josephson. “The 

226 TRUE GENIUS exchanges went back and forth several times, with Josephson answering each criticism of his theory. The scene was quite civil because both men were soft spoken.” But as Morrel Cohen recalled, the two “seemed to speak different languages.” “Bardeen was outspokenly skeptical,” according to Wolfgang Klose, a professor of thermodynamics at the University of Kassel. But “Josephson did not give in.” When Bardeen said that he believed Josephson’s idea “was quite impossible, Josephson repeatedly asked Bardeen, ‘Did you calculate it? No? I did.’” Josephson won the debate. Afterwards, Klose noticed, “Bardeen put his arm around Josephson, like a father to his son. In this attitude they left the lecture-room.” Josephson later explained that “Bardeen’s basic error was to ignore the non-locality inherent in the Gor’kov theory, and assume a local connection between the potential and the pairing.” The issues would be fully spelled out in 1963 in a paper by Anderson and John Rowell, a Bell Labs experimentalist, who observed the tunneling supercurrent predicted by Josephson. Anderson and others explained the Josephson effect within the framework of Gor’kov’s formulation of the BCS theory. Two months after Anderson and Rowell submitted their paper to Physical Review Letters Bardeen wrote to Anderson. “Your evi- dence, particularly the effect of a magnetic field on the super- current, is quite impressive.” He suggested that to reconcile his view with Josephson’s it was necessary to take “into account the superconductive energy gain from the matrix element for pair tran- sitions across the barrier. . . . It is this energy that I did not take into consideration in my previous estimates of the possibility of a tunneling supercurrent.” Josephson’s effect was now certain. In July 1963 Sidney Shapiro published a paper reporting “several startling accompaniments of the Josephson effect.” Later that year Bardeen publicly withdrew his opposition at a conference held in August 1963. Two years later Josephson accepted Bardeen’s invitation to come to Illinois for the academic year 1965–1966 as a postdoc in the many-body group. While there, Josephson wrote a now-famous paper on the second- order phase transition to the superfluid state. The Josephson effect has had important practical applications. Two of the most prominent are SQUID (Superconducting Quantum Interference Device) magnetometers that can measure very weak, 

Two Nobels Are Better than One Hole in One 227 almost static, magnetic fields and switches based on Josephson junctions. Bardeen’s colleagues sometimes went out of their way to show their appreciation for him. In 1968 the physics department threw a gala sixtieth birthday party for him attended by many friends and col- leagues from around the world. Bob Schrieffer created a work of art as a birthday present for his mentor. He “sent off for little photographs” of all of Bardeen’s students. Then he “cut out small bodies from brown felt and made them hold violins.” He arranged them on a large poster board. It included “John in a set of tails with a red sash as the superconduc- tor in his grand canonical ensemble.” Bardeen hung the collage in his office. Another unusual gift came from John Van Vleck, who distributed to all the dinner guests a microfiche card containing Bardeen’s collected life’s work. “Makes one feel humble,” Bardeen wrote. George Hatoyama of Sony Corporation, whom Bardeen had be- friended on his first trip to Japan in 1953, brought a remarkable golf ball created specially for Bardeen. The gift was designed to recog- nize Bardeen’s work on the transistor and to commemorate the many happy times Bardeen had played golf with his Sony friends. The size and shape of a normal golf ball, this one had a transistor radio inside with a tiny speaker and a rechargeable battery. In later years Bardeen would sometimes use the golf ball radio in lecture demonstrations or to play tricks with it on the golf course. In one trick, he would replace one of his opponent’s balls with the radio, so when the person arrived to make his putt, the “magic” ball would be playing some radio station. Bardeen’s hesi- tant manner did not lend itself to joke telling, but he would often express his impish sense of humor in such practical jokes. In time the radio developed a loose connection or short that made it necessary to squeeze the ball or hit it in just the right way to make it work. “I will have to take it apart and repair it,” he wrote to Hatoyama. In the fall of 1985 he accepted Hatoyama’s offer to have the radio repaired at Sony’s service company. By Christmas he was using it again to entertain friends or to illustrate transistor history. In 1971 Bardeen directed James Bray and David Allender, his 

228 TRUE GENIUS last students, to a controversial problem involving a new mecha- nism for superconductivity. In this picture the attractive electron interaction responsible for the state comes not from the electron– phonon interaction but from the virtual excitation of electron-hole pairs. Bray confessed that he had no concept of the complexity of this excitonic superconductivity at the time he began work on it. But he knew that when Bardeen offered a problem to a student, it was “not just to throw you into the wolves” but “because he had an idea or two.” In fact, Bardeen had “an outline in his mind of how to pursue the excitonic superconductivity problem” and worked on the problem right along with them. When it came time to pub- lish, he insisted that his name appear last on their joint paper. One day later that year, Myron Salamon, one of Bardeen’s Illinois colleagues, recalled, “I was sitting in coffee hour up here in 208 MRL [Materials Research Laboratory] and John came and said, ‘Have you seen this? We really ought to get involved.’” Alan Heeger at the University of Pennsylvania (who would in 2000 win a Nobel Prize in chemistry) had just announced his discovery of the con- ducting organic, one-dimensional material, TTF-TCNQ. He believed it was superconducting. Salamon and others measured the ratio of the thermal to electrical conductivity (the Wiedemann- Franz ratio). They “showed these results to John,” who happened to be nearby looking at his mail. “I said, ‘We’re finding that the Wiedemann-Franz law holds’ and he looked up and he says, ‘Oh, I guess the entropy is a constant of the motion.’ And he walked away.” Salamon asked Bray, “What does this mean, what’s going on here, how can this be? What is he doing?’ It took us a week, and we figured out what John meant.” Bardeen had an intuitive idea for explaining charge transport in the exotic material, which was later shown not to be super- conducting after all. He proposed treating the transport in the one- dimensional organic system like current-carrying sliding charge density waves. The idea harkened back to his earlier work on super- conductivity in 1950. Heeger’s discovery opened a new field of research on “lower dimensional materials,” which would be exten- sively studied for their nonlinear properties. These materials, in which charge is transported along long molecules, are among those that exhibit charge density and spin density waves. Because Bardeen recognized the opportunity, “we jumped in,” said Bray. Subsequently Bray studied the “excess conductivity in these one- 

Two Nobels Are Better than One Hole in One 229 dimensional organic systems.” Bray and Allender finished their thesis work in 1974, shortly before Bardeen retired. In the early 1970s Baym and Pethick were working on the theory of superfluid 4He. They were puzzled by the question of the momentum carried by a “roton,” a short wavelength excitation. “So we went to John,” who they assumed had thought deeply about this. “And indeed he had.” Bardeen answered their question in the form of a riddle. “Well, it’s just the same as the difference between B and H,” he said, the two forms in which the magnetic field is expressed in Maxwell’s equations. “We had no idea what he meant,” Baym confessed, “and it was very difficult to find out.” They made several attempts to decipher Bardeen’s cryptic remark, but eventually they put the question aside. About a decade later Pethick and Baym were trying to under- stand the long-range magnetic interactions between electrons in metals. “So we went back to John for advice.” Again he replied, “Well, that’s just the difference between B and H.” Again they could not understand his meaning. “But the second time was different because he gave us a reference, the review article that he and Bob Schrieffer wrote in Progress in Low Temperature Physics.” The article, written in the late 1950s, included a discussion about the difference between B and H, but the meaning was still unclear to them. “Fortunately, I was going to see Bob Schrieffer in two days in Santa Barbara, so I took along a copy of the article,” Baym said. He was excited as he walked into Schrieffer’s office. He expected to learn at last what the difference between B and H was all about and how it could inform problems like the roton or the magnetic inter- action between electrons. “I showed it to Bob and said, ‘Okay, explain to me what this means.’” Schrieffer laughed. “Well, John kept saying that all the time, it was the difference between B and H.” He turned to Baym and said, “I never understood what he meant, but he insisted we put it in the review article.” For some time after that, whenever members of the group encountered a problem whose explanation was obscure, they would jest, “Well it’s just the difference between B and H.” Then all would chime in with a resounding “Ahh!” People began to murmur about a second Nobel for Bardeen. Nobel 

230 TRUE GENIUS prizes had been awarded for lesser achievements that BCS, but no one had ever received two in the same field. Bardeen was concerned that, if the Swedish Academy of Sciences held to tradition, his first Nobel Prize would rob Schrieffer and Cooper of theirs. Bardeen was pleased to learn in November 1967 that Schrieffer was to be awarded the American Physical Society’s Buckley Prize. This was not technically an award for BCS but for work done in the last five years. “There can be little doubt, however, that Schrieffer’s contribution to the microscopic theory was a significant factor in the award,” Bardeen wrote to Charles Kittel. Bardeen raised the idea of awarding the Comstock Prize of the National Academy of Sciences jointly to Cooper and Schrieffer. “The Comstock Prize is more significant than the Buckley Prize, so that a joint award should make up for any slight Cooper might justifiably feel in regard to the award of the latter to Schrieffer alone.” Bardeen’s prodding worked. The 1968 Comstock Prize was awarded jointly to Schrieffer and Cooper for “contributions to the theory of superconductivity.” Still Bardeen continued to feel Schrieffer and Cooper deserved a Nobel Prize. He decided to do what he could to arrange a Nobel Prize for BCS. His Illinois colleague Charles Slichter believes he “came to realize that the only way to get a Nobel Prize for that was to arrange a Nobel Prize for something that came after it and depended upon it.” Bardeen gave the idea some thought. He “realized that the thing that really appeals to the Nobel Prize com- mittee is to have an international group.” Superconducting tunnel- ing was the natural subject. The work depended on BCS, for Josephson’s work build directly on the BSC theory; Giaever’s work allowed seeing the lattice vibration spectrum; and the Eski diode is based on the tunneling effect. If such a prize were to go to Leo Esaki, Ivar Giaever, and Brian Josephson, the laureates would be Japanese, Norwegian, and British. In 1967 Bardeen proposed a Nobel Prize for electron tunneling in solids, “an area that has had an extremely rapid development in recent years.” He wrote to the Nobel Committee: Those I would like to nominate are Leo Esaki for his discovery of interband tunneling in semiconductors and the tunnel diode, Ivar Giaever for his experiments on tunneling through a thin oxide layer separating two metals, particularly when one or both are super- conducting, and Brian D. Josephson for his predictions concerning 

Two Nobels Are Better than One Hole in One 231 supercurrent flow through a tunneling junction. All three of these discoveries have opened up new areas of research. He renewed the nominations in 1971, 1972, and 1973. The tunneling prize was awarded in 1973—to Josephson for his theory of superconductive tunneling, Giaever for his tunneling experi- ments, and Esaki for the observation of tunneling in p-n junctions. And the prize for BCS was awarded a year earlier, in 1972. “John was a very politically savvy person,” Slichter pointed out. “People have a concept of John Bardeen as being kind of an innocent unworldly person. I don’t think that is correct. I’m pretty sure that John Bardeen figured out how to get the Nobel Prize awarded for superconductivity.” Bardeen first learned that he had won a second Nobel Prize in physics from a Swedish journalist who called his home from New York on Thursday, October 19, 1972. “I didn’t quite believe him,” Bardeen said. “These things are often false rumors.” But around dawn the following morning he was awakened by the official call from Sweden. Once again great excitement ensued in Champaign-Urbana, whose physics Nobelist was now a double laureate! A stream of reporters questioned Bardeen about superconductivity and every- thing else. When he tried to leave for work that morning, his elec- tric garage door opener failed. Newsweek and other magazines and newspapers focused on the irony of the transistorized apparatus failing to work for the man who had invented the transistor. Bardeen hastened to explain that what had failed was not the tran- sistor but the switch outside the door. “I’ve got my wife working on getting it fixed.” (He had, in fact, disconnected the transistor because it was so sensitive that airplanes passing overhead were causing the door to open.) “We’ve had that door for years, and it never failed us before.” When Bardeen finally arrived at the university, he attended a lunchtime seminar about David Lee’s study of superfluids at Cornell. The only difference from the usual brown-bag affair was the champagne ordered by David Pines and Nick Holonyak. A reporter followed Bardeen to one of his classes. A number of colleagues and other students also attended, for word had gotten around that Bardeen would speak on superconductivity. “At a few 

232 TRUE GENIUS minutes before the hour, Bardeen entered the room, head down. . . . He glanced at his watch as he reached the front of the room and began. ‘I think this would be a good time to discuss superconduc- tivity,’ he said with a small grin.” The reporter also attended a press conference at which Barden “spoke softly, slowly, almost re- luctantly. It was almost as though he wondered what all the fuss was about. But he had the look of a man who is so happy he can hardly stand it.” On the Saturday following the announcement, John attended the Illinois home football game. “Bardeen put on his overcoat and hat, wrapped an apple in a paper towel and drove to Memorial Stadium to watch the Fighting Illini (0–5 at the time) play Michigan.” It was reported, “Bardeen does not miss home games” and, according to colleagues, “he roots like hell.” The usual round of congratulations followed. John smiled broadly when Nick Holonyak teased him that all he needed now was “another Nobel Prize with two other guys and you’ve got a whole Nobel Prize.” Hundreds of good wishes flooded in from friends, colleagues, and people Bardeen had never met. Brattain wrote, “Sorry you could not get your garage door open!” He said that he and his new wife Emma Jane would be thinking about him on December 10 and added, “Be sure you don’t need to buy or bor- row a dress shirt at the last minute.” John replied, “Jane and I have been going over the souvenirs of the 1956 trip which reminded us of the marvelous experience we had. It is a surprise and somewhat overwhelming to be going again after 16 years.” The board of directors of the Champaign Country Club, led by George Russell, one of Bardeen’s golf partners and that year’s presi- dent, wrote: “I know we are expressing the feeling of all club members when we say that such a richly deserved reward couldn’t happen to a nicer person.” Another admirer complained in a tongue-in-cheek editorial sent to a local paper about the amount of publicity John received for the second Nobel, compared with the publicity garnered by other university employees. “Let’s keep these things in perspective. A Nobel Prize winner comes along every day, but a new football coach or athletic director is a once in a lifetime story.” Bardeen tried to respond to all the letters, but in the end ran out of time and patience. He took special care to answer letters from young people, such as one sent by eighth-graders in the school 

Two Nobels Are Better than One Hole in One 233 where his nephew taught art. “Being eighth-graders,” they told him, “we are really interested in your first Nobel Prize, which dealt with the transistor, since most of us use transistor radios.” A nun in Brazil shared her fuzzy but fond memories of working with a scien- tist named Bardeen in Pittsburgh during World War II. “I would be so pleased if you turned out to be that same gentleman!” Bardeen wrote back that she had probably worked with his brother Tom, who lived in Pittsburgh at that time and had children like those she described. Jane again chose a blue formal gown to wear at the ceremony, this one of crepe with princess lines and “very pretty beading and embroidery.” Recalling King Gustav’s scolding in 1956 about leaving the children home, she insisted that this time they all come along. By now the three children had spouses, and there were two grandchildren. It was a great family reunion. The trip began on December 4 with a minor crisis. Due to icy conditions, their flight from Champaign was cancelled. Pines saved the day by suggesting that the university supply a car and driver to get them to O’Hare Airport in Chicago. “The roads were good shortly north of Champaign-Urbana,” Jane scribbled in her diary, “so we arrived at O’Hare in good time.” The next day Jim and his wife Nancy met John and Jane in Copenhagen. They gave themselves two nights and a day “to catch our breath and get used to the change in clock before the swirl of activities in Stockholm.” The rest of the family arrived in bunches throughout the day. On December 6 the entire clan had lunch with Aage Bohr and his wife Marietta. Later, John and Jane paid a visit for tea to Aage’s mother, Margrethe Bohr, Niels Bohr’s widow. On arrival in Stockholm on December 7, they were immedi- ately sucked into the Nobel activities. Jane enjoyed sharing them with their children, Jane’s brother Jim Maxwell and his wife, and their friends the Gaylords, the parents of Bill’s wife Marge. Jane was delighted to have so much family present, but wrote in her diary that it left “almost no time to shop or just wander thru the city as I did in 1956.” On December 10, the day of the presentation ceremony, Bardeen led the procession with Stig Lundquist, a physicist at the university in Göteborg, Sweden, who would later become chair of the Nobel Committee. As they proceeded into the hall, Jane noticed that “John’s shyness caused him to hang back so that L had to grab his hand and pull him forward.” Gazing into the 

234 TRUE GENIUS audience, John focused on his family—Jane, three children, two daughters-in-law, a son-in-law, and two grandchildren. “We were quite a crew,” he told reporters, chuckling softly. “They took up quite a bit of the front row at the presentation.” Bardeen handled part of the huge job of answering congratula- tion letters while they were in Stockholm. Jane had made up a combined thank-you and season’s greetings card, which they both signed. When John later wrote to thank Carl Vernersson of Rank Xerox Sweden, who contributed a secretary to help the Bardeens mail cards, he added, “If your profits show a sharp drop in Decem- ber, you will know the reason why.” On the way home to Illinois, the Bardeens stopped in Switzer- land, where the children skied and John and Jane enjoyed the moun- tains. They also stopped off at Murray Hill to participate in a small Bell Labs reunion dinner in honor of the twenty-fifth anniversary of the invention of the transistor. Jim Fisk, now president of Bell Labs, had added a note to the invitations, saying that “John Bardeen’s second Nobel Prize for his work in superconductivity provides an additional reason for rejoicing at this time.” When the Bardeens finally returned home, they found a letter waiting from the Wisconsin Telephone Company informing Bardeen of their intention of naming December 23, the anniversary of the day the transistor was first demonstrated to Bell Labs execu- tives, a statewide “John Bardeen Day.” “Naturally, all of us at Wisconsin Telephone are proud of the research contributions you have made for the good of mankind.” Bardeen responded, “I have always had a very warm feeling for my home state, so that this very special honor is greatly appreciated.” The many-body groups at Illinois and Bell Labs continued to compete with one another. Bardeen had always enjoyed the com- petitive spirit inherent in cutting-edge research, but the quality of the exchanges sometimes disturbed him. The Allender, Bray, and Bardeen paper on excitonic super- conductivity gave rise to another challenge from Jim Phillips, who in 1968 had left the University of Chicago to join the many-body group at Bell Labs. He and Bardeen had exchanged several heated letters about the work during September 1972. They were unable to agree. Phillips then wrote a highly critical response and sent it to 

Two Nobels Are Better than One Hole in One 235 Physical Review Letters, which, because of an editorial blunder, was published on December 4, nearly two months before the Allender, Bray, and Bardeen paper that Phillips was objecting to. Phillips’s letter undercut the paper’s reception. Bardeen found the letter waiting when he returned from Stockholm. He was livid at this “inexcusable set of blunders,” Bray later recalled. It was “the only time I’ve ever seen him actually say mad cross words out loud.” Early in January 1973 Bardeen wrote an angry note to Samuel Goudsmit, the editor of the Physical Review: “An author certainly has a right to see his article appear before a distorted and misleading account of it is given elsewhere.” Goudsmit wrote back that the editors presumed “the author must have been in contact with the authors of the cited paper and gotten permission to quote from it.” Responding to Bardeen’s suggestion that the journal “establish procedures such that cases similar to this one cannot occur,” Goudsmit replied, “I do not know how this can be done without the help of the F.B.I.” Karl Hess remembered eating lunch with Bardeen and Bill McMillan shortly afterwards. McMillan remarked that things around the department had been a little dull of late. Unaware of Bardeen’s most recent exchange with Phillips, he said, “Shouldn’t we invite an interesting person?” He innocently suggested Phillips. Hess watched a red wave of anger travel up Bardeen’s neck and into his face at the mere thought of bringing Phillips to Illinois. “Poor McMillan never knew what he did.” The Bray-Allender-Bardeen paper on excitonic superconductivity caused a few more waves later that year when Phil Anderson and John Inkson wrote a critical comment on it for Physical Review Letters. Allender, Bray, and Bardeen replied that Inkson and Anderson had misunderstood the paper and had dealt with “semiconductors with different physical properties.” The comment and reply were printed back to back. The two groups continued to argue without resolution. Anderson felt that Bardeen was not reading his and Inkson’s comment accurately and that he had grown too stubborn to consider that someone else might be right. They finally “agreed to disagree.” Such controversies were tempered by activities such as golf. Allender, Bray, and Bardeen often played golf together. “I got better while I was his graduate student,” Bray reminisced. “If a real nice day popped up we would all look out the window,” and if the 

236 TRUE GENIUS weather was right, “We would just migrate as a whole” to the uni- versity golf course near the airport. “It was fun playing with him. He was the usual gentleman there that he was everywhere else. Not terribly talkative there like anywhere else. He was a very good golfer. He usually would beat us.” When Bardeen learned that Allender’s father was a golfer, he suggested that when the senior Allender visited Champaign they make a foursome with Bray. The older players scored much higher than the younger ones. Back at 55 Greencroft, Bardeen took out his Nobel medals to show Allender’s father. “It was something my father would remember all of his life.” The hours of physical activity in the outdoors helped Bardeen relax and reenergize. He rarely used a cart, preferring to walk the roughly four miles of an eighteen-hole course, and managed to avoid becoming as rotund as his father Charles had been in his later years. Golf provided Bardeen with an opportunity to express some of the attributes that also made him an excellent swimmer, bowler, billiards player—and great scientist. The golf course was another domain for mastering challenging problems and developing the “mental toughness” ascribed to the best golfers. A nongolfer might imagine the game of golf as a leisurely stroll around the greens, but it was nothing like that for Bardeen. Every stroke demanded control. Golf also required focus for long periods, both within a single game that might last four hours or more. Over the years Bardeen pursued the sport at every opportunity. Like scientists, most golf- ers experience months or years of consistent and relatively un- eventful practice, punctuated by a few brilliant successes. The better golfers develop a core of realistic confidence and optimism that allows them to execute complex skills consistently and keep them in the game over the long term. In the short term, reinforce- ment (both positive and negative) is immediate, for a ball either does or does not do what is wanted. A player’s game suffers if he or she becomes discouraged over a series of less successful shots or overly excited by any one thrilling moment of success. Although Bardeen liked pitting himself against others, the important competition was against his own skill level and previous scores. He was a favorite golf partner at both the country club and university golf course. He had a slight tremor in his hands (possibly the result of a high fever in his youth) that worsened with age, but it had surprisingly little effect on his golf game. Jim Bray, who 

Two Nobels Are Better than One Hole in One 237 played golf with Bardeen regularly in the 1970s said: “He’d get out there and start swinging his golf club as if nothing were wrong at all. He would swing very smoothly and very well.” Bardeen, said another golf partner, “never rushed things, not even his golf swings.” In his middle years, Bardeen shot in the high 70s, a good score for a man with a fairly sedentary lifestyle. Even in his sixties and seventies, his scores fell respectably in the low 80s. Bardeen enjoyed the social aspects of golf almost as much as its mental and physical activity. He cultivated numerous golfing friendships at the country club. One foursome consisted of Bardeen; Charles Keck, a local merchant and amateur cartoonist (among other talents); Myron Kabel, an agricultural products sales repre- sentative; and King McCristal, a professor of physical education. Esther Werstler, whose husband was another regular partner, ap- preciated the fact that John never failed to ask about her work at the hospital. John “never gave me the feeling” that he did not want to include her in a game because she was a woman. In December 1969 Kabel had a heart attack (from which he fully recovered). For a get well card Keck drew a cartoon of the other three golf buddies shivering on a golf cart at the first tee of the country club while waiting impatiently for their friend. John is saying, “Call him again!” Keck is wishing he had a bourbon, while McCristal merely says “Br-r-r-r.” For his golf partners, John was just another good golfer. His scientific renown was not an issue. Charles Slichter treasured the story about when one of Bardeen’s longtime golf partners at the Champaign Country Club turned to him and said, “Say John, you know I’ve been meaning to ask you. Just what is it you do for a living?” Slichter commented, “I think if I had won two Nobel Prizes like John has, I would manage to work it into the conversa- tion somehow!” Several of Bardeen’s golfing friends complemented John’s reti- cence with their ebullience, in the same way that John’s brother Bill, his friend Walter Osterhoudt, and his colleagues Brattain and Holonyak did. Paul Coleman was highly entertained one day watching the large and garrulous Louis Burtis energetically man- age a golf game while Bardeen cheerfully acquiesced. Bardeen continued to derive an element of fun from golf, even when not on the greens. One spring day in the late 1960s Bardeen and his colleague Harry Drickamer were chatting at a reception. It 

238 TRUE GENIUS appeared that the world was flying apart. Students everywhere were protesting U.S. involvement in Vietnam. The National Guard had been called into Urbana-Champaign to maintain control. Jane Bardeen had broken a vertebra in her neck and was wearing a brace, and Drickamer’s daughter had recently had orthopedic surgery. “Boy, things aren’t very good, are they?” Harry said. “Noooo, not so good,” answered John. Then, after one of John’s characteristic long pauses, “a little smile comes to the corner of his mouth. And his eyes turned with them, ‘You know, Harry,’ he says, ‘I’m shanking my iron shots and when that happens nothing goes right.’” After his second Nobel Prize, Bardeen began to prepare for his retire- ment, set for March 1975. Having taught for more than twenty years at Illinois, he looked forward to spending all his time on re- search. When new students asked to work with him, he politely explained that he would not be able to see them through to the end of their work and did not want to leave them hanging. Ravin Bhatt was one of those students. He came to Illinois from India in 1972 hoping to work with Bardeen, but Bardeen was no longer accepting students by the time Bhatt had completed his early course work. Although disappointed, he felt better after Bardeen referred him to McMillan. “If it couldn’t be John, Bill was about as good an advisor as I could get.” McMillan directed Bhatt to prob- lems of superfluid helium. When Bhatt finished his Ph.D. he went to work at Bell Labs, just as McMillan had done a decade earlier and Bardeen had done after World War II. Bhatt felt that by working with McMillan he “inherited some of the style of physics that John initiated.” Bhatt took the last course that Bardeen taught, Physics 463, an advanced graduate-level course in quantum fluids, one of Bardeen’s favorite subjects. It was an intensely demanding course in a tightly circumscribed area of current interest—the kind of advanced course for which the Illinois physics department was famous. Students were expected to immerse themselves in the literature and practice problem solving with minimal guidance. Hoping to take advantage of the last opportunity to take a course with the double Nobel laureate, about sixty students signed up. Under normal circum- stances the course would have drawn fewer than ten. As most of 

Two Nobels Are Better than One Hole in One 239 them were ill prepared for the work, Bardeen’s teaching method quickly reduced the class to about the usual number. Bardeen’s retirement called for a celebration, but Ralph Simmons, then head of the physics department, had to take into account Bardeen’s “great distaste for any formal retirement festivi- ties.” He compromised by turning Bardeen’s retirement party into a symposium on “Frontiers in Condensed Matter, held on October 15, 1976.” The menu of the symposium dinner listed: “Poulet Polyphase, Champignons Champaignoise, Boulettes au jus Stockholm, Crabe Etat Solide, Consomme Jeanne, Bouef Bardeen, Pomme de terre Laureate, Tomate grillee transistor, Salad Plusiers corps, Petits Pain PNP, Sorbet Superconductif, Beverage aux choix une ou plus dimensions.” The program also included the texts of several songs composed by David Lazarus. One verse, sung to the tune of the “Battle Hymn of the Republic,” went: There’s been BCS and APS And PSAC too Pals like old TI and Xerox. (Don’t you wish that it were you?) P-N junctions made transistors Wigner’s training sure came through. Our John keeps marching on! (Chorus): Place your bets on the electron. Pairs and singlets you’ll conject on. Nobel Prizes you’ll collect on. Our John keeps marching on! After becoming a professor emeritus, Bardeen continued to work in his office almost every day, spending some time in the physics library studying recent articles. He still left his office door open to invite colleagues and students to call on him with their problems. John Miller, a graduate student of John Tucker, Bardeen’s collaborator during the mid-1980s, remembers that Bardeen was “amazingly up to date” on the latest theoretical and experimental work on charge density waves and high-temperature superconduc- tivity. When experimenters asked Bardeen for help with interpreta- tion or design of their experiments, he brought to bear his “really encyclopedic knowledge of solid state physics.” 

240 TRUE GENIUS Among the few changes that colleagues noticed in Bardeen’s patterns after retirement was that he stopped regularly wearing a tie to the university. After the second Nobel Prize, he seemed a bit more relaxed, somewhat more outgoing. “You feel more self- confidence having received a Nobel Prize,” he told a reporter. He was more likely to spend sunny afternoons on the golf course. And one could more often find him sitting with his feet up on his desk in a pose that recalled his days at the Naval Ordnance Laboratory more than those as a distinguished university professor. He more readily indulged in relaxed chat with colleagues. In fact, it became increasingly difficult for his colleagues to extricate themselves from such conversations, even to get to their classes on time, for Bardeen would sometimes discourse at length. In his seventies, the man who had spoken so little throughout most of his career became, now and again, almost garrulous.