EUGENE GARFIELD INSTITUTE FOR SCIENTIFIC lNFORMATION@ 3501 MARKET ST, PHILADELPHIA, PA 19104 The 1987 Nobd Prize in Physics: Citations to K.A. Miller and J.G. Bednorz’s Seminal Work Mirror Developments in Superconductivity
Number 18 May,. 2, 1988
The 1987Nobel Prize in physicswas awardedto two researchers,Karl Alex Miiller and Johannes Georg Bednorz, in the field of superconductivity.Accordingto ISI@data, their key paper, which has garneredthemmuchacclaimas well as the award, showsan unusuatlyrapidcitationaccumula- tion. Other aspectsof this fieldare covered, includingpreviousNobclsawardedfor work in super- conductivity,and a Citation Ckmic” commentary by SovietphysicistA.A. Abrikosovon type II superconductors.
For the seventh time in over 40 years, the 1973) to raise the temperature of sttpercon- physics prize has been awarded within two ducting materials 19.3 kelvin (K), from 4 years of completion of the research recog- to 23.3. Absolute zero on the Kelvin scale nized by the award. A scant five months is equivalent to minus 273.15 degrees elapsed between the publication of Johan- Celsius. nes Georg Bednorz and Karl Alex Miiller’s The 1973 achievement by J.R. Gavaler, seminal paper, “Possible high Tcsupercon- Westinghouse Research Laboratories, Pitts- ductivity in the Ba—La-Cu-O system, ” 1 burgh, Pennsylvartia,d remained unsur- and their Nobel nomination;z eight months passed until Bednorz and Miiller’s January later these two scientists from the IBM 27, 1986, discovery.s The two researchers Zurich Research Laboratory, Ruschlikon, worked with a new class of superconduc- Switzerland, received the 1987 physics tors (involving oxide-ceramic materials that prize-the shortest time lag in NotM history. are usually semiconductors) that hastened a According to the Nobel committee, when further breakthrough to the 30 K plateau; Bednorz and Miiller less than a year later, in 1987, physicists measured temporary superconductivity phe- at lastbrokethroughall exisdrtghits for nomena between 2006 and 5(X)7 K. supercorxiuctingmaterials,it wasas a re- The 1987 physics prize marks the second sult of systematicwork, deepinsightand year in a row that Nobel Prizes have been experienceof structuralproblemsin the awarded to personnel at the IBM Zurich Re- physics and chemistryof the solid state (plus,onemayassume,theintuitionchar- search Laboratory. In 1986 Gerd Btig and acteristic of the true scientist). Besides Heinrich Rohrer won for their 1981 inven- this, theyhadthe audacityto concentrate tion of a tumeling electron microscope.B on new paths in their research.g The discovery of higher-temperature su- perconductors widens their use in diverse The 1987 award has highlighted art ex- applications-such as medicine, transporta- traordinary year in this area of physics. tion, oil exploration, energy storage, nuclear Bednorz and Miiller’s work has electrified research, and computers. the low-temperature research cmnrmmity— Citations to Bednorz and Miiller’s most- for it took scientists 62 years (from 1911 to cited work mirror closely the relative calm
129 Fiiure 1: MOST-CJTED PAPER. Bimonthly citations The portent of this discovery for small to J.G. Bednerz end K.A. Miitter’s “Pnssible high ~ science is significant. Even laboratories in superconductivity in the Ba-La—Cu-O sysrem, ” Z” Phys, B—Co&fens. Matter 189-93, 19s6 small schools and institutions everywhere can conduct basic research that has direct 250 relevance to new technology. 2 0 “s~ 200 Biographical Sketches of u 150 the Nobel Laureates % & 100 n Miiller was born in 1927 in Switzerland E 50 and received his PhD in physics at the Swiss $ Federal Institute of Technology, Zurich, in 0 b 1958. He joined the IBM Zurich Research Laboratory in 1963, where he presently works in solid-state physics. Bednorz was born in the Federal Republic Month and Year of Germany (FRG) in 1950. In 1982 he also received his doctorate from the Swiss Fed- eral Institute of Technology. In that same year he joined the IBM lab at Riiscblikon. and the subsequent explosive advancements The two are corecipients of severrd pres- in this specialized field of physics over the tigious awards, including the 1987 Fritz past two years. As of early 1988 their paper London Memorial Award of the University has garnered over 800 cites, Figure 1 depicts ~f California, Ims Angeles; the 1987 Dmnie the growth of citations to their paper over Heineman Prize of the Gdtingen Academy a 14-month period. of Sciences, FRG; the 1987 Robert- “It is very satis@ing that our work has Wichard-Pohl Prize of the German Physical generated so much interest and has been rec- Society; the 1988 Hewlett-Packard Euro- ognized by the Swedish committee .... We physics Prize; the 1986 Marcel Benoist never thought about the prize, ” commented Foundation Prize of the Marcel Bertoist laureate Miiller in a Physics Tbday inter- Foundation for the Advancement of Scien- view. “We only wanted to go beyond the tific Research; and the 1987 Viktor-Moritz- intermetidlic A 15 compounds.”9 Table 1 Goldsehrnidt Prixe of the German Mineral- lists their most-cited works. ogical Society. Bednorz and Miiller’s breakthrough came from a “small science” project in an era of Physiss Phenomenon multimillion-dollar, frequently gover- nment-sponsored efforts. Their tools were Superconductivity remains an only partial- simple, consisting of a standard cooling ly understood effect--despite its discovery flask, mortar and pestle, a scale, a high-tem- urthe early twentieth century. Bnaically, su- perature oven, some voltmeters, and a per- perconductivity is a phenomenon in which sonal computer. For scientific establish- materialslose all their resistatw to electrici- ments in developing Third World countries, ty. Therefore, such materials can carry cur- this is a heartening example of world-class !ent without producing arty wasteful heat. research on a limited budget. According to Scientistshave compiled a list of four criteria Nobel laureate Abdus Srdarn of the Third hat help identify a superconducting mate- World Academy of Scienees, Trieste, Italy, iah (1) a total loss of resistance to a direct “Any nation can still join this potentially :urrenq (2) expulsion of a magnetic field rich yet still-open quest if it can afford just Fromthe material’s interior (also called the $30,000 for equipment and money for the ‘Meissner/Gchsenfeld effect” after its dis- physicists’ srdaries. ” 10 :overy in 1933 by Walter Meissner and R.
130 Table1: HfGHLYCITEDWORKS OF mR AND BEDNOIU. papers with Karl Alex Miilter end/or Jobannes Georg Bedrrorz as Srat author or coauthor. A = number of citations. B =bibliogrephic citation. The SCP research fronts to which the paper is core are included in parentheses.
A B So6 Berfnorz J G & Mrdfer K A. Possible high TCsuperconductivity in the Re-la—Cu-O system. Z. Phys, B–Corr&ms. Matrer 64:189-93, 1986. (87-0892) 151 MutterK A & Berffngar W. Static critical expmrcnts at strucrurrd phewtransitions. Phys. Rrv. Mt. 26:134, 1971. (73-0957) 143 BroutIt, MrfferK A & Tkornae H. TumreUirrg end colleaive excitations in a microscopic mcdel of fermekxricity. Sol&i .Wte Co-. 4:507-10, 1966. 128 Skrrarrek E & iWdJer K A. Covalency and hy@inc structure constant A of ircm group impurities in crystals. J. Phys. Chem. Sdirir 31:102740, 1970. (85-6017, 847549) 125 MnUer K A, Berfirtger W & Waldner F. Characteristic structural phase transition in perovskite-type compuunda. Phys. Rev.fat. 21:814-7, 1%8. 101 Etednorz J G. Takaslrke M & Mufler K A. Suaceotibditv measurements sumrurt high-T. superco-tiu~vity in ~ Be-La-Cu-O system. kurop~ys. Letf. 3:379-851 “1987. C87-6892)
Gchsenfeld, Physicrd-Technology State Itt- Bedrtorz and Miiller’s breakthrough. This stitute, Berlin, Germany); 11(3) high repro- map demonstrates that most of the research ducibility of the phenomenon; (4) high sta- emphasis was on theories of how particles bility of the phenomenon (superconductivi- (such as electrons, protons, and neutrons) ty observed in the sample for periods of days interact during the superconducting state. or weeks in the proper environment). The map’s center is defined by research All four of these criteria have been met front #86-0707, entitled “Heavy fermion su- in some of the new copper oxides 1’2(with perconductors, heavy fermion superconduc- combinations of barium, strontium, fluorine, tivity, and superconducting UBe13.” A fer- lanthanum, yttrium, and oxygen) at the 90 mion is an atomic particle whose spin quart- to 100 K range; zero resistivity and a par- tum number is an odd multiple of one- tial Meissner/Ochsenfeld effect have been hrdf. 16 seen at 225 K; partial resistivity has been seen at 290 K; a drop in resistance and some How Superconductivity Heated Up other faint indications of superconductivity have Iwm observed at 360,1340,14 as well There have been three antecedent Nobel as 5007 K. The new oxide superconductors, awards in physics coneemting suWrconduc- such as those discovered by Bednorz and tivity. It is interesting to note that low-tem- Miiller, are type II superconductors perature research dates from the nineteenth (materials that exhibit two separate threshold century, but it wasn’t until the early part of levels in the expulsion of an applied mag- the twentieth century that scientific methcds netic field)-always alloys and compounds, and apparatus allowed for the intense study excepting the rare-earth elements niobium of phenomena occurring near absolute zero. and vanadium. 15 The current focus on oxide-ceramic ma- Kamerlingh-f%nes terials is only a small part of a very large field that encompasses research in supercon- One of the premier researchers in ductivity. Table 2 lists the 1986 research low-temperature physics at the turn of the fronts explicitly related to the subject. The century was Heike Kamerlingh-Omes C2-level multidimensional scaling map on (1853-1926), University of Leiden, The superconductivity in FQure 2 shows clusters Netherlands. He is widely regarded as the of research fronts, rather than clusters of grandfather of superconductivity. He and his journal papers, as would be the case in a associates discovered the phenomenon in Cl-level map. Twenty-six research-front April 1911 while working with a sample of clusters on this map show the state of su- supercooled mercury at 4 K (usually liquid perconductivity research during the year of at room temperature, the sample was frozen
131 Tabfe 2: SUPERCONDUCHW’TY RESEARCH FRONTS. ‘fire 1986 SCP /SSCl@ research fronts on suWrcon- ductiviry. A =number of core papers. B =nmnber of citing papers.
Name AB
86-0128 Heavyferrnion superconductivity and arrisotropic magnetic bcbavior 9 91 86-0130 Magrrctic field penetration depth in superconducting UBe13 and magnetic 10 63 superconductors W-0424 Superconducting transition region in TaSe3, superconductivity in amorphnus Cr fdms, 2 11 and quasi one-dimensional conductors 86-0522 Superconducting nctworka, phase transitions in a disordered granular superconductor, 2 17 arrd twodimensionafarrayof Josephson junctions 86-0524 Superconducting BaPb.XBix03 (BPB) ttrin fflma, bipolaronic superconductivity, and 21 173 defects in amorplmus selenium 86-0594 Heavy fermion superconductivity and heavy fermion behavior 3 33 8641rlnl Electrorr-phmron superconductors rmd electron-phorron irrtcraction irr metafs 8 125 WM3616 Enhanced superconductivity in quasi two-dimerraionaf systems 2 26 86-0707 Heavy ferrnion superconductors, heavy fermion supcrcomiuctivity, and superconducting 49 462 uBe,3 865727 Supercmductivity in granular ftis arrd electric conduction in copper gatfium telluride 4 85 ehirr ftis 86-08179 Thin superconductirrg Nh fdms sml twc-dirrrensiorral superconductivity 2 30 86-1191 Superconducting fflms arrd noncquilibrium superconducrnrs 4 30 86-1467 High T, A 15 materials, superconducting NbN, arrd mriveraaf disorder-induced transition 14 68 in the resistiviey behavior S6-2094 Organic corrductors arrd superconducting BEDT-TTF salts 45 293 86-2449 Antiferromagnetic phase transition and superconducting ternary compounds 5 29 84$-3238 Fine-grained Pb afloy fdms for Josephsnn integrated circuits 6 36 86-3311 Magnetic heavy fermion superconductor URu#~ 4 30 86-3470 Layered metals and upper criticaf field in supacondrcting srqrcrstmctures 3 20 S&3678 Supaconrfuctirrg vibratirrg reed in a longitudinal magnetic tield and flux-line lattice in 5 24 type f3 supcrconductnrs Superconducting CCrnrrrymolybdenum chafcogenidcs and phase field of the chevrel phase 344 PbMo
solid). 17 Kamerlingh-Otmes was awarded Cooper-Schrieffer (BCS) microscopic the Nobel Prize in 1913 for his low- theory of the superconducting state in terms temperature research. of “Cooper pairs” of elextronsl g and the From the 1930sinto the early 1950s scien- Abrikosov theory of type II superconduc- tists were able to raise the superconducting tivity. 19 temperature of materials to 18 K. Develop ments in rhe understanding of the how and Bardeen-Cooper-Schrie ffer why of superconductivity reached a mile- stone in 1957 with two papers presenting In 1972 John Brtrdeen, University of Illi- two major breakthroughs: the Bardeen- nois, Urbana; bmn N. Cooper, Brown Uni- .-
132 Ptgrrre 2: SUPERCONDUCTIVITY RESEARCH, A multidimensional scaling msp for C2-level research front #f16-W57. The size ofthecircles is deterrnkd by the total number of cites received by the core papers in the research front. Amorphous Thin wperconducting ferromagnetic films 5161 mstals Heavy fermion superconductor 3311
Elmtron.phonon Field.induced ,ee”t, ant supar. superconductors
Photoemission spectrs
2012 I ntormediste valence Twodimensional superconductivity Conducting Magnetic supwconductom or~nic saltr
Hssvy f wmion systems
0088 Mstallic systems
Superconducting 1533 chevrel phnssr Single crystals tnd chevrel compound%
versity, Providence, Rhode Island; and electron attracts nearby positively charged Robert J. Schrieffer, now at the Institute of nuclei of the lattice. A second passing elec- Theoretical Physics, University of Califor- tron will be attracted to the excess positive nia, Santa Bahara, were awarded the phys- charge created by the higher density of ions ics prize for their famous “BCS” theory. in this puckered region and is thereby in- This hypothesis contains a general theoret- directly attracted to the first electron. This ical framework that describes superconduc- weak attractive force binds the two electrons tivi~ in terms of a condensation of electron into a so-called ‘‘Cooper pair. ” The paired pairs, and thus the theory is independent of electrons have opposite spins and equal and the specitic nature of the attractive forces opposite momenta, so that the net spin and involved, Indeed, the BCS theory applies not net momentum are both zero. One result of only to conventional superconductors, but this is infiite electricrd conductivity-a su- also applies to superfluid helium 3, to su- perconductive current carried by Cooper perconductivity in neutron stars as well as pairs is believed to persist forever.zl This in atomic nuclei. In each of these cases, the classic paper, entitled’ ‘Theory of supercon- transition temperatures (when the material ductivity, ~~18has been explicitly Cited Over goes superconductive) vary from millide- 2,800 times since its publication in 1957. grees to millions of degrees kelvin.zo The BCS theory, prior to Bednorz and For superconducting metals the BCS Muller’s discovery of superconductivity in theory basically posits that an electron basically semiconducting materirds, was moving through a metal’s czystrd lattice thought to be correct for all materials. The tends to distort or’ ‘pucker” the elastic lat- theory now seems to hold for those materials tice slightly because the negatively charged that are superconductive below 50 K, but
133 Figure3: RECENT DEVELOPMENTS IN SUPERCONDUCTING MAT3XUALS. Historiogrsph ahowing developments in this research. Numbers of cordciting papers are indicated rrtthe bottom of each box. Asterisks (*) indicate re-ch frOn~s in which BcdcroIz and Miller have core pcpcrs; research tiorrts that they cite into are indicated by &ggers (t).
85-0866 Properties of glassy amorphous films 7/1 05 t87.6264 Relaxation asmicmrduetors t86.0524 and high Tc oxides 854412 Supereondrretirrg Properties of mstsl 211243 oxides, bipolar. supercmrductor-sami. mric superconduc. conductor trarrdtions t87.1973 tivity, and glassy 74-6551 High-temperature super. 5/30 systems Superconductivity of conductivity and metal 211113 oxides snd carsmics ssmicmrductor transition 6/34 65-6509 83-0991 71112 Anomalous properties Optical and chemicsl of narrow zone high- “87-0692 proprmtiss temparsture supercOrr- High T= superconductors of orgsnic ductors and bsnd electronic molecules 2/15 84-7373 structure adsorbed Ferroelectric phass- 28/1 ,093 on metal = transition and other 854872 turfaces electrical properties Study of electronic 12/69 of pure and doped band structure in Pbj ~Gsx Tearrd alloys Pbl ~Srrx Te 3/21 H 1 3/1 7J 1 3{73 I for those materials that show superconduc- theory. This dk.inction has often been ig- tivity above 90 K, a different, unknown nored or confused in the literature for mechanism appears to be operating.21 more than 25 yars.20 However, Schrieffer disagrees with this assessment: Abrikosov There is growing evidence that the so- called BCS theory is likely to apply for The second key paper that appeared in the oxide high-temperature supercorrduc- 1957 was authored by A.A. Abrikosov, tors such as that discovered by Bedoorz L.D. Landau Institute of Theoretical Phys- and Miifler as well as the higher- ics, Academy of Sciences of the USSR, temperatureoxides that have been dis- Moscow. Entitled “Orr the magnetic pr~r- covered more recently. At issue here is, ties of superconductors of the second what is the specific mechanism of attrac- group, ‘‘19 this paper has garnered 1,300 tion Ixmwerr the electrons? It is my belief cites to date. In a Citation Classic@ com- that the arrtiferromagnetic correlations in the copper-oxide plane play a crucisd role mentary22 on this work, Abrikosov writes in providing the attraction. However, that regardless of what the attraction might he, a condensation sc in the original BCS My acticle wss published in 1957. But it theory, I believe, is stiff fnndacnecrtally the -was ordy in the early 1960s that it was underlying mechanism prcducing the ef- “discovered” by physicists in cocmection fect. Thus, it is essentird [to] distinguish with the creation of high critical field al- between the general theory of supercon- loys. I am not surprised by the frequent ductivity provided by our original work citation of my acticle. The superconduc- and the specific mechanism of attraction tors of the second kind with high criticaf which can be encompassed by the general fields are the basis for the construction of
134 superconducting magnets, which are at Their breakthrough came later, from Bed- present the main technicaI application of norz reading about ceramic experiments, superconductivity. published in 1985, by the chemists Claude Michel, L. Er-Rakho, and Bernard Raveats, Josephson Laboratory of Crystallography, Chemistry, and Physics of Solids, Caen University, In 1962 Brian D. Josephson, University Frartce.2TThey created and studied a com- of Cambridge, UK, published a paper en- pound of lanthanum, barium, copper, and titled’ ‘Possible new effects in superconduc- ~xygen. However, the French researchers tive tunneling.’ ’23This work, cited in over did not study the sample for superconduc- 650 subsequent publications, presented his tivity.zs In January 1986 Bedrtorz and theory of how electrons tunnel through con- Miiller did so and discovered that it had su- ductors to become superconductors. One of perconductive properties-although it took the theory’s tenets is that if two supercon- an improved version (using different pro- ductors are separated by an insulating fdm portions of the elementszg as well as a dif- that forms a low-resistance junction between ferent manufacturing processzb) in April them, Cooper pairs can tunnel from one side 1986 for (he sample to exhibit sttperconduc- of the junction to the other. This theory has tivity at the then-unprecedented temperature great import in the computer industry where of 35 K. Figure 3 is a historiograph high- superfast switching elements exhibit the lighting research activity in metal-oxide ce- “Josephson effect. ” Josephson won the NO ramics from 1983 on. It is interesting to note bel Prize in 1973 for this work. However, that Bednorz and Muller’s’ ‘superstar” pa- the eponym attributed to thk phenomenon per appears as a citing work rather than a undoubtedly will be remembered long after cited one in 1986. The full impact of the the award is spent .24 journal article on the field of superconduc- tivity came later, in 1987.
GoMmskii Worldwide Impact of Bednorz arid Tumeling in temperatures near absolute Miller’s Paper zero is not a phenomenon singular to supe- rconductivity but also occurs in chemical When the Zeitschrsjl jilr Physik B— reactions. Vitali I. Goldanskii, Institute of Condensed Matter published their paper, it Chemical Physics, Academy of Sciences of was first greeted with widespread skepti- the USSR, recently reviewed this subject in cism. The physics literature is cluttered with Scientij$c Arrrerimn in a paper entitled preliminary and unsubstantiated claims for “Quantum chernicai reactions in the deep high-temperature superconductivity. How- cold.’ ’25 ever, in the words of the Nobel cotnmitlee, The idea of looking for superconductivi- this paper “was the start of an avalanche. ty in the class of ceramics called perovskites Hundreds of laboratories all over the world (a structure type in which physicists have were soon at work with materials similar to great interest, since slight distortions away those of Bednorz and Miiller, ”3 from its standard cubic symmetry by out- We can trace the influence of Bednorz and side influences may result in ferroelectric Miiller’s classic paper directly to supercon- properties) occurred, according to Miiller, ductivity research efforts taking place at cert- while he was sitting in the garden of a ters all over the world. medieval monastery in Sicily during the Since January 1987 temperature achieve- summer of 1983.26Miiller’s moment of in- ments have exploded, with monthly press spiration led to his work with Bednorz on conferences reporting preliminary experi- various oxide materials in late 1983. These mental results. The press conferences are efforts, however, did not yield immediate held because the flurry of experiments has outpaced the rate of publication for tradi-
135 Figure 4 SUPERCONDUCTMTV PAPERS. Annu of superconductivity is that the new mate- dk.tribution of papers reporting on superconductive rials are now more accessible and less cost- over the past five years. ly to use. In the past superconductors had 2,000 to be cooled to much lower temperatures 1,750 E with liquid helium, which costs about $2.90 g~ ,500 (US) per liter. The new metal oxides are able 21,250 to use the more abundant, and cheaper, liq- ~l,ooo uid nitrogen, which is about 6 cents per liter.Jo Despite difficulties with the fragili- j 750 ty and brittleness of the new oxide-ceramic g 500 materials, scientists are making progress in 250 the manufacture of flexible wire, the use of 0 the superconducting new materials as coat- 1963 1964 1965 1666 19S ings,J 1 as well as the use of explosively Year generated shockwaves in the creation of ce- ramic/metal alloys .32 tional journal articles, which often take If 1987 activities are anv indication. 1988 year or more to see print. Instead, researck will see advances in su&conductivity of ers are sending papers-’ ‘preprints’ ‘—d similar magnitude. Already in the early rectly to each other. In response there hav months of this year laboratories in Japan, been initird efforts to publish solid-stal the US, and Europe have achieved a fiuther physics journals more quickly. I might adc temperature breakthrough to 120 K using however, that the preprint phenomenon ] copper oxides that contain the elements not new to physics—it is accepted practice bismuth, calcium, and thallium.JJ To ascertain the impact of Bednorz an This essay illustrates what can happen Muller’s discovery on the superconductive when two scientists think unconventionally. ty literature, we used ISI”’s SCLSEARCM However, this is just one of numerous ex- database. Figure 4 depicts our findings— amples where researchers defied the as- shows that from 1983 to 1986 an averag sumptions of their day. One old myth that of 900 papers were published; in 1987 thi comes to mind is that the noble gases are figure zoomed to 2,000-spurred, in pan inert. Neil Bartlett and N, K. Jha, Universi- by Bednorz and Miiller’s primordial paper ty of British Columbia, Vancouver, Canada, Research laboratories in over 40 nation discovered in 1962 that xenon was reactive on all continents (excepting Antamica) hav with fluorides. 34 Bednorz and Miiller’s progressively raised the temperature for st decision to look into semiconducting perconductivity. According to 1S1data, tb materials for superconductivity phenomem top 10 countries that have published papex reminds us again that today’s common on superconductivity are (in descendin wisdom was yesterday’s folly. order) the US, Japan, the USSR, the FRC the People’s Republic of China, France, Ir dia, Switzerland, the UK, and Canada Other nations include South Korea, Israel Belgium, Egypt, Brazil, Taiwan, Libya Greece, Argentina, Poland, South Africa Yugoslavia, Mexico, Sweden, Saudi Arabi: ***** and Hungary.
Superconductivity’s Warm Future My thanks to Peter Pesaverrto for his help One benefitof the almost fourfold inereas in the preparation of this essay. in the threshold temperature for the ons~ $,9W,s,
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