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Pee pagation Jounal of Seizres Communion 41 100 Years of Superconductivity Partl Abstract Sierconductiigy is w phencmenon of excite zero law hractane semper fis coovere 9) Heike’ Kameriingh Onnev in 1941 at Letden in Water. Like ferrcmaametios and tame specead fins. superniede is" @ gursan mechanical phenomenon i maenoscope scale Iris charactenoed by 11) Zero resisiance 6) Pension: Ciopent 2) Perfect ‘homegnetinn d) Hs quanatation ane e) Baer ap. Sewers necsesgiuattenss were meade since cas Mts explain te phenornen even Ey pst ie Btn Heisenberg und Feynman, saat the Theory of Siverondheti iy yas nacho by Barve, Cooper un 57 ie the US. fn the. nec mand, conpibcions tows anontanding the siporeandecthit was mele By Messmer Cchsenfo London & Lozdon. Fritch Manweil Reynolds ula oup of Sover phsciis inctting Lacon Gitabun, Hniosor, rkos, Bogolvubers and ethers. {8 Gather mlevone, the Jasephvow Tmeling, ons reached ‘Uniden, “becaa of the egatiment of vers temperate sper hs eran ereing topic eccasvonay disease in poster classes, Witt the uiscovery of gh Fr rcondutoss, Bick eam operate a fig moyen limporaraes (77 Kj. supercondactiyy 1 nos el | hin the scope for prectoatapptcaton Even. hit ‘schon stuensseas etpore ad experiment with snow And inpcrtantrecholoveal eld of plysiee The Part | ofthis part ait races the ump ide ter he | tnderstanting of the theory of superconduc from | BAN io aheue 1982 The second part wil seas the ‘tema of UCN sheory Tope ll supecunductors \osephson Eee, mgt. sipensendcniy, recent © deepmens and some applications, _ Discovery | The sory of saperoonductvity ean be truce ace to | tne early 19th esnsary with scientists being able to uel In 1893. Paraday distovered. that _tseus chlorine ould be liquefied by 2enerating ist "ih pressure at one end ofa scaled alass lube and iWatthe ac end, With a good understanding ve behind the liquefaction, Faraday sean to liquey every ‘known gas. is metiod ant itsuments vere erude, nevertheless, he suceeded Frqetsing every kina gis, nth tte exceptions sanygen. nitrogen, and Iydzoger. “nS? French ‘VOLUME 3, NO. 1, JANUARY, 2012 Indranil Sanyat Physicist Louis # Cailetet, ind Susy sclentst Rao Pictot independent y suecseded in liquety ing both oxygen end nt But their yield was se small” Before that achieverent. any in the Fig tele Kamneslingh Seioatifie, community anes assumed tt those. Bass lore wis perhaps iqueluction, By L883, Karol Olszewski end Zemut yon Wroblewski in Cricow had sucvected ‘lleting cubic centimeters of liuid wnyen, ard nilrogen. hn 1862, Tleike Kammerlingh Ones yout professor af Teiden University, suseccdec, in developing an apperatis for producing thore in large (quant ties. The sestem tank aay eaage of what beeae nown asthe cascade process, The univ wes remains {o be conquered was hydrogen, as helium as Uunknewn, although its exisense ia dhe Stn Was ‘own, The liquetacton af mydroges develope toa bone of eontention between Heike Karserlingh Ones aw Sir James Dewar, the Seotsh low-ternperat physicist. 1998, Dewar, succeeced 10 igiety lhyctogen by taking advantage uf 4 hermdynemie cffeet know Joule Thomson cxpansion. 7a Fhg2. Kammering Omes crigina plot ol supercandcting 42 P-. pagation . Losing the face for Tiguelving hydogen to Devas, CGanss developed rhs rs helium iguefis i 1908, nieresirgly, Holium ou d= Fath was discavened flyin 1935 by the Edalsh chemist Wiliam Rams Gn taly 10, 908, he sucoessfills Liquefied stium by vol nst-0 264 dogrees below sero egress Celsius (4 Kelvin or 4 <), The aiseqve'y opened the door to an etre realm oF passibiity involving law lemperatare fespetiments. ‘Tus was the fst S.eeesTul allem a Tigueiyny helium which provided a ne lersperatar ‘approaching absolve zero, Ketmelingh-Oanes "work a vory low tenperstures just a fe Alegrees above the absolute ver af temparature. He sucesedeal in reching temperatures ch co der thas {yanebefors him and thus opened a new font toe Science, te eld of fot temperature plsics, Ke snd covteseutciers Gilles Holst, a stent entrust by ‘Onnes with precise resstaneé measaremenks, nd G. Flim “he lesbain responsible for the helium Tiquelter ise, pertinent the experzrens to sluly wh eppened u aris properics et aerials when they sere exttemely cok. Helst wis studying the clscrieal resistance of wires, Te Tound that a he ‘eoled meroary wit, the electsesl cesstance of the Wie woke an aorupe dtop when he got to abot 3.6 {degrees aboxe absnline es0 The chop ws enorrious the resistance became et Leas twenty thousand tines sullen The crop "ook place ove a temperate interval top smal for theat to measure. As Tar they fuuld tel, the electrical resistance completly venished, Non-superconductive Metal “— Superconductor Resistance OK Te Temperature Fig3.Low te pendant esistne inNowmal and Soperurctingtsatrals Previous ests ha founc tat tke resistances fell texponentilly as the fermperatuce appewacked zero. It had bees knew far many’ years tthe resistance of metas fell wien cooled below com sempenasir, but eas not known what Timing value the resistance ‘would approae’, i the etperiare sere reduced to ‘ery lage to 0K. Some sets, such ae William in, believed that slechos Rowing. though conductor would coms tos eompets bal “he temperature approached. absolute 2er0. Other Soles, ireluding, Kameringh- Onn, felt that a Cold wires resistance would dissipate. This sugsen ed that there would be a steacy decrease in eects resistance, allowing for better conduction of lecticiy AL some. very Tow teripersure. point, Scents fit bat there vu he a leveling ef Bs he Fsitinee reached some Mile yed anu vaue Allowing the cuenta flow with fleur esstans Tinwever. the testing of merery Woke the mation, ‘anes foul ata 423 clgrees Kelvin, the resistance of mercury fell sharply Lae Kemrlingh-On Sescibed then enomenonas At this point somewhat below &.2 KI vtthin some henareths ofa deere eame aster al not foreseen by the vibrator theory of resistance tha had Been framed. bringing the resistances once less than ion of serial vale atthe msttng po “Mercury had passed inte anew stat, whichon aevoent aftsextraordinar elec cal properties may bead the superconductve state, Fig (1) shows Oars orca ph presented daring is Nobel Lecture To expan why resi depended on emperatine tall Ontes cura ‘tibers Hinstin. recent icv nf quantum ‘ciltors, cevised in 1906 to xplcin the toe Specie nets of sols Ite etal se aims ver tat pede the ow oF ent a ‘hese ost ations seca smaller ow fneraue {5 Einsein wo pode, tea Einsehvsonct nae might sapin the wey restuncetiminkhed Th Tul alow temperance Ths pare pruit “srshetansoa regent asthstonerane apprnached DK. trover stv of sparc mucl weld ‘ah toward seb. Toto is ace Omer chose terry. whch could be punfind by din Maton ea sch tas expested-o hates h yh cooughestoarce inmevarentai Repeated trials sonvineed Ques Eat the sudo loss ‘of moreur's resistance a abour 42 K ss eeal The resul: was Gist presented by Ones al te fs: Solvay Conterenes, he'd in Brussels from Detar seth 10 November 3d, 1911 under the tile "On the Sedasn Chanetn she Raroat Which the Resistance of ore Disappears” He tepurted the work ct hs faborlery lide: is own rare lene, without co-authors. Holst ever gor credit for discovering supercondhcts iy. ‘Pe. pagation “om of Sen Commision Subsequent fests of in end lead shoved that Superconductivity was a property of numrous metals ithhey were covled stent: Figurs(2} ise raph? fesstnce versus tecaperature is noemal as well as Superconducting materiel. By 1914 Ones established a permartent eurent, or ‘what he caed @ “porsisent super ewrenl” in fpereonduecng coil br ead, The eoil was placed in a fyosat at ln romperatue, wih the carrer? belie inlosed hy an este! sakgnelic Feld, Wilh a0 revises, the clectwns in the coil were free to owt To low indeiritely, In one of Kameengh= Onnes experiments, he slirted ¢ curmect owing ‘Wop lop ot lend wire cooled ta 4 KA year lor cient a sil ssi without significant sureent ‘Gas tated that the sale could be destnyed ily lage magnetic fed wile a 04 loop of supervonductie ke supiying s suffice arent inenced io & bre persisted for an extraordinarily Teng tite. Le fkmonsrated the Tavsephosometon by saris Superconducting current ina ceil ih hs Leiden Tatoiaery andl dren suspoctiy the oll plas the retigeraton, which kept it col, Universiey Tora Tectare demonstration on Supsreonductivily, Physicists were making piltr mages to Teen ta observe the conceivable! Desisteat cuteat in logp of supersarudacting wi filing with 4 eommen magnet needle, ve Cambridge anes report de wot cause much strat that ime, ut ‘Onnes recognized the importante of his discovery 0 the scientific community as well ay its commereal Pate, An sleevieal conductor with xo resistance ful cary earcutfa sy distance with a Tasses. I IisNobel Prize spoech in 1913 (he prize wis awarded Metals “Transition temperature Lend (Ph) 196K Lantus 488K ic) Taran a [447K Mereury (ig) [415K Tin (Sn) 32K Indiv tnd 341K Table I: Superconducting Transition Temperature fae 43 for his tescarshes om bslium), Onnes underlined tre anexpectec. peuple othe desrese i resistanes, By 1073, itwes eslaished it the same phenomencn, naw calecl ihe sipereorudctire stile.” accurred ‘a ad i but Dot gold and platinrn. Ia subsequent decades other snpereoadveting. metals, alleys and bompaunds were d scaveved. In 194] sigbiamentride ‘eas found to apr eonlect a6 In 1953 va silcon displayed supercendieive properties 17.5, ‘in 1962 selena at Westinghouse Coveleped ies comercial superoorsieting. wire, a slley hicbium cod ctaniuin NLT. [Tate L shows Superconducting, Transition Tenperure For some meals} Meisxner Effect: The Next Revolution ‘The Flst Work War boough a temporary. break, in low temperate research liga became. unavailable it Europe. it restated in 1919 ‘with gift oF 8 cubie reter Huliui coming feo the USA. Teli as abundant jn the Unived States The Teiden group resumed wore bo. sunercanduc-ivity discovering wnumber of new Superconducting elements inline, inven, ete), and also studying the eaghetic properties of supesconductos. fu 1923 heliunt was quefod in Toronto unt J.C. MeLensan. Lo years er, in 1925, Walther Meissner in Berlin stared iguid-hetian fener He sis eager te fot One fgrcupinLsidon, tu Finally onmed Fisww foaich at Berlin wae remarkable disco ew classes of supercorslacting slemonts, loys and then el comps Fi 4 Waller Meissner in 1933, Max von Laue, the Gestugn Nobel Laureate, Suggested to. Meissner” an experinent designed to Hltermine wheter the cuireat in suereondnesor Slows on is suiface or in ils bulk. Meissner chose Soner Oehsonfeld'n cary ou de experiment. other Suprise they found that'@ superconducting mater ‘epelsamagneti fiend excluces t completely trom itshull Ths ncasthal sy brat al bar magne up toa supevcanducte, the superconehcior bends the Hino of free away tr taal doce alos em £9 penctiat "This phenomendn is known as perfect lamapoetisny and is today often referred tts the Meissner effect” and is. very popular demonstration of supeteonductivity. The Messner fact js 80 strong that a magnet cen uetually. be levitated 44 over a superconductive materia, The Meissner Effet ‘illocer onyitthemagictie eds relanvely sal Tie magnetic std heecmes tou gre, Hp the inlror of the metal aude ml foxes is Suetcuadacuvty THe magnetic fk vanish nth interor af bulk speci eveu whe ene down hrtow te munition tperatne ine presence a magnetic Bei. The iamagrots currents wich flow inavhin petation layer nee the Surtice of simple conzected Body to thsi the iene om at extents applied! ste ae stable nher than foetescble. Or the or Fand. persistent currents Towing ia mun eonteted bud eye a lon are ‘1 T<To TeT¢ FigS Diamagnetc propery efasuperconicte= An American, FB, Silsse Leidsn dash, supe-eende had suggested (using iat lhe observed reakdosn of ityina magnetic Feld wes sullicien 10 explain why supereanducivity. was also. destroyed Wen the sample carved 2 very lange elects eure the eurrent sinply created the necessary misanctie fickl Tue Leiden gevup verified Silsbee’ hypothesis They slbo developed thesttong caavetion tha, when» sample became suporeendhcting, whalever magnetic tax was already aro bssarsefozen in, andl other ‘ehanges in ux through the sample would be excluded by the perfec: conductivity. Thus the msgnetie state of the sample was not reversible, 30, thal mo ‘icrnodytaanic analysis could e applied. ‘The result vvas Wdramitic ane unexpected. vex ‘alien ihe tn slinders were pot carrying any curren, tie magnetic Field between thom incfoated hen they were cooled ‘mo their superconducting stare, The fhozeneia fx ‘dea was not corect ard theexclision of applied this was not nietely 4 dynarvies! effect of perfoe Enndueriity, Superconductors were not wily perfec findutors, they were also ‘pericet damages ‘Mathematically, ye obain a particular y ust! Terr fof thir sult if we Ginie ourselves to. lone Specimens with long xis parallel to Bsn the lemougnetizing field contbution to. B willbe eglisibe, hen ult BAO cannot he derived trom the ‘thanacterizarion of @ superconductor ac 8 median of ‘zsroresistfvty, From hits as, E=p, ean be easily Shown that ithe res stivtyp goes zero wile nie then I mms he vow, By Wlaxwells cy, dBc proportional ta err F so that aero resistivity pls wldr0. “This predicts thatthe flax themgh the mal ‘eanrot change n couling through the mastion, The Meissner et ect conics this reat ard supts that pe-fectdiamagnetis: is an essential eepery of the supsreonducting sta Electrical & Magnetic Properties of Superconductors Since shere is no Joss in electrical energy superconcuctois cany electseal Curent, relatively harrow ws md of supercorsucting wales ch bbe used to carry huge currents However, there is ertin maxinoum coment that there mates cin be fiuds to cary, ahove ‘whieh they stop hein Supercaneuctors IF too mien simrent is) pte tisough a suscreond teri wll revert fo the Hos slate even thongh it maybe below is transition ‘euperature. The vse of Critical Current Density (_)t8 4 Tuncton af remperatures tre coker $0U aperconiuctot the ore current ean “ary eal applications, J. values in exeess of 100 per scare uillaneter (Aram) are prefered, AAs closrioe een ins wine eroesamagntic eld ground a wire, The sicengih of she magilic field Jeases athe erent in the wre inereases, Recane Supereendhicrars age able to cary rpe eurcens ‘wnat loss oF enciay ey ane well sited for making Soong lecromagnots, When a supereondactor 1s Cooled below its transition temper Tndgnetic held increased aroun i, the niggnete Tield remains aroune the supereonducio. Physicists uke the capital Tener Yas the symbol for Magnetic Field the rngnetic elds inereased to a given pot the superconductor will li ornal esinive st PTT Peee ee eee eeeeee Pr. pagation Adour! oS {he masimurs value Zor the magnetic field ata given tmpertie is known ae the Creal magnetic fla and ib given the symbol H. For al supereonductors ‘here exists 8 min of tempecatures and magnetic Fld within wach the materia i superonsdactng Oubidethisrepionthematerialisnormal ‘Wher te emperatute is lowered to below the ei ‘emperaiur,(7), the superconduetoe wall “push the field out of Self. It does this by crating, surface cen in self which peoduces a magnetic Held sey countering the etesnal Geld, producing a "mggneic mivoe", The superconductor becomes perfsly dtmnagneti canceling ll magnetis ft in fs intr Thi. pe-Tect_cssnagaetie propery of Sineronhictors is perhaps the most funeamentl macroscopic. property al 2 supereanductor Flux fxclsion du fe what is referred wa the Miisner fo, canbe easily dernonstated in the classe by Towering the tenpesatuve of the supersonductor to below is 7 end placing a Small magnet over i. The nagaet will bepin to fla: above the superconductor fn host eases the ini! megnetic Hed From the mag et ing on the supercoractor will be stron engh Tint sorte of the field will penetrate the material, resling. in -mom-supercandacting region. "Tne ct therefore will net levitse a igh 8 0” inouced afer the superconductive sate hes bo chained. Early Attempts Towards an Explanation Before iediscovstyof he Meissnereffet,atternpsta mike theoretical progress. in explaining $ipetcandit iy, particularly by applying the newly {seated qusstunttory, aude ie press. Ir real, therewas ne chance fer anyone to Selve:tispreblem at thetimeot discovery because before ons could explain Ione Bats nave the quaatra theory n the form st Schsktnger md Heisenbers develope. hich did not Luke place unl the 1920s, Fort long time the ig. Priteand Tans London 45 nomenon of susewauacivity wes shiraetviced estalcment that th clselicl resistance vanished completely AThert Einslein in 1922 cone ued thet ‘Roary wnat yet upto theta Bonvoen 1928 and 1933 Felix Bloch, whose doctoral toss in 1928 gave the tnsie theory of conduits i ‘otal, worked onthe problem tages with Wolteaas Pauli and Lev Laren” Nicls Bohr, Nemer Hester saul Leon Hriloin also jomned the oH, but thot The discovery of the Meisner Freel was 1 eucl turning pon. Supcrcorductivity ull coud ol be sxplained it tom of quentam mechanics, bot the thermodynamics of the phenomenon was tinlertandele Pan Fhvenfest who believed tat Teswomunivy God pe teed sae me anes ‘scnmaon tt ernsuet le ar Bsa mice (ses eyed Conc Ge 9 Salen ct ee Ht iia rm lacs coms poe to ous we Rend toy evay tone Cor wel Got ahead to ful oly eco tC aber eu tei puss naiion at ans a ‘SStmnnmic fpr post th cr ar ee rd stat te crpennt PD fers a facton i of he Seaton cal fa Gebel haag coke Boe SSperd” whch i pay esque er te rsmcabie perso seconds le FBovcuay cocoon osetia ca erations The un Bp, es weal Som zo Toto nig TO, whee al ot tie ether sein esmpetl condensate [A seeond inode themes wlvanse came i de following yea, when bothers riz and Hats Lona, oo efvgees dum Nasi Germany, atthe Clarendon [aborts at Oxford, propose ther phenomenal theory of the electomagneticy properties of superconductor, in whieh the diamagnetic rather tha flere pecs wore ussursel te Bemors funda. In fn olny metal we dere the shenemenen of loecal resistance by the fous Ohm's law. What the Tol bras cid wats fo shew tht thre ws annthar rhamatealrelsioship which shouldbe od in plsse fof Ome Law to serie superconductors, Trot this ‘other eltonship waich they developed. they ware able tw explain hth the Mrissne-Ccer fel expen swell atthe persitonrcun to Kareingh-Cnns as 60 roanifstations ofthese sthin, ‘They sugaestsd thatthe eloctricalovrent density j curred by tie suport isteated tothe cleric Held E 46 P< pagation and magnetic field Rat ech point in epace by two TLondan equations expressed in forms of measurable fells a, ot om Hore 4, the superconducting current, Hane B are respective the lest and maghetie Fie with the Supercond cores the charge of unelectron& proto, nivis election mass, and N, Is a phenemenslogical Chrstant loosely asneiated With @ Humber density of Superonndueting crsers, ne . ne F “The Pvo equations ean be samhined to farm a single “London auation” in tam of the magnetic yeclor potena AV A is ta be chosen suck the V0 wo ensure current ‘Sonsevation, Ifthe socond of London's squntions is ‘anipulated by applying Ampere’ aw aj VxB=> ‘hen theresultis the ditferentil equation iB 2k (es ann,e VB “Therefare Rs) Bye “Thus, the Tondon equations imply a chanscterstie lerath Seale over whieh external magreti elds are ‘xponenticiy "suppressed. This value athe Landon pee ph ha tat a rage el Gisunce which sooner of 10" ce in typcal Superconductors for well below T, Observed vas “otfearehoweversevera imesthe Lénon val. Front Londor: theory the iiportane phennmrena of ux fqurization cay be sauly understood. We corset HceaStpereonduingeng. espn helo aie Supcteometor the is compleeey Sekced cut, th “heros, super currents should be absent there he fintt~0 Inrodocing super eutentdeasity and reartanging we . faat [fas bs ig themagneti Ane throgh the rng, We see Sen, that themanee xc isquanited 2mhe #02 nbs inumtsofthe Mux quantum: == ee candensation ofthe average moments dstibution” Development Between 1950-57 ‘The Second Werle War interrupted research in supercencuctvity just as the First, World, Wor had Sone. It wes aot uh sbout 1950 tat real progress began ones again to be made, The phenomenc cil resisted ary tue microscopic understanding, ut some hicces of the purzle did heuin to caste (ogelhes, perioulary mn the phenomenological model of Vitaly Ginsburg and Lev Landau. Ginzburg and Landay (1950) extended the London plenomenolagy int Priliat stroke based en Landat’s theory of seocad agation Alsi of Save Commision SERRE EREEEE EERE ERE EE ES 47 nlerphase reasons. does not pupert to expan the iMictescupie. mechanisms BIving. niet fupetconductiity. Ingtsady ic exeiines. the Inatesepiepropenics of «superzantor with the hid gata hernacsmnio argument Ths theory insometies eal ed phemomerolngie” sit deseribcs sonco the pheroneta of superset iy thot ‘Aplaning che nersing eerscopic mectanisr Buse on Landauspzeviouls-etanishod theory of secomurder piso tansians, Landa and Ging.ua Iated that he ow energy Fo asipereondcoc at ie stpercondicing Wauiion cat Bs expressed tsa eamps ocr pst hich Gesrbes dow deep int hespetcadicing prose rhe syste. The foe enety hat the form we Fi the ive np cit -zeay| lO = ole Slot a5 energy inthe rommal phase. @ and ff are pientmenologieal pacameters mis an effective miss, isthe chage of an elects, A isthe magnetic vector pots and Bouck is The imagnete field. By he fee eneruy with respect o fluctuations Parameter and the veetor poten, ae evesatthe Ginsburg. Landau equations a + BIPPY + 3b (ihV-20Ay¥—0 we (ifV - 2eA)y} where j denotes the eleetcal suront density and Re the real pari. Tho first equalien, which Deals inercstingsimilarives te the time-independent uation, determines the order paraaseler ‘applied magnetis field. The second thes prosides [ie spetconductin Equation futon Thistheory ws ners by Geko 105) tb hea limiting ease of tie BCS tauey and remains today ashe standne initial appoach to pubes wit spills varying superconducting stats, The veel sipfizance ofthe wavs functioliks order parameter ‘vould net be explained until the microscopic BCS theory came along towa'ds the end of the decade However even aller the BCS theory provided a Iniemstopic understanding of supereoaduedvily, th ‘much simpler id easiero-ase Gincburg-Landsa moti remained (and remains) the every-day working hoory used by theorist and experimertalsts ale t0 snaly7> all manner of eamplex phewmena in superconducti rm] Fig? Wiely Gincburp(le®bondLoy Landa Annimportant concent wae rtrudcedby A.B. Pippard fin 1983. Aided by watlime development in high {recuency technclogy. Pippurd was abe to sake very precise msesuromenis of ho compare with London Eqcation, using parameters determined fo. similar measurements of th skit dept the normal state metals Fe toond tha, event =U, the hited value of yeas less than the desty of corduston elec on the aomal sate, by'a ratio a was arger “oel0% spaterialslikeal (7= 1K} han fo: metals like P(e 7K), He concluded that « "cohersnee Kong” is ‘sociated wit) the superconducting state ich Chat a pertushetion of the superoenductor ata. point Decessily influences the superthuidwihin adistence 2,0" thatpoine For pure etal, 3-10" ct. for T= Tle generalized the Londor. equation to & abn-luedl forct nl accounted fer thetuct that cho experimental ‘alue of *he penetration depth is sveral times lager han the “London yalue.” Suosequemty. Barusen sued that Pippares aop-loel rstion Would likely follow fromancnrgy gp mee Perhaps the single most iesportant experiment wish directly played wriding role to an explastion of Supereonactiviry sens the experiment onthe "sot tffect" This oocured in tha spring 0f 1980, Pa fom ta taboratories simaltaneotsly reveal he same result One paper avis bv Reynoles, Seri Wight and Nesbitt at Rutgers Liniversly. The whet vsas by F- Maxwell at the U.S. Nasional Bureau of | Standards. Roth groups measured the ansison leamperatures of separated mercury sotopss and that in meteor yT, wares fin 4,156 toe 40K a the average atomic mass M varies Tn! 195 (0 2034 ‘42m. The tansition temperature changes staoethly a> tfffrentsotapes ofa same element mined Tis reult behavastarie elation: M'T.=Constant ‘Sultans rn ca azs007 He SDH 08 Pb 9.0 02 | Zn 045.005 Ze one.08 : Tile 2 Observed alucs oF Tor isaupe ele Soperoondustors 48 Ir; pagation From the above relation and data between T, ans) snipe mass, wean understand tat Jatice vibiation td slecinnla tice aration ace elewely vlad bo Superconcuctvity So wt the Hsolopie experiments ta talked abun showed otha although the lscreal conductivity was known te arse because of {he moson ofthe elecizons, there's some ale of these Ince vitwaions ‘They enable the eloctrans snddenty 1 move through the lates, evidently without Irind-ance, when che sample Ts cooled tothe critical superconducting temperature. asthe elementary discovery thar transition temperature depends an murnher of neleons. the mass bro lanes imporsat, het mesian and ts the aie: Vibrations mint he fie. Independent, Brisk physicist Herbert Prhlich, sso was thon spending the Eprny term sf Pardue University, aorpedtn develop theory of superconductivity taned onthe self enero {Melgctnsin the Reldot phonon. He aed abou! the isotepeeffct in mite May choy before he sented his paper fox publication aid was clighed to find very sir experimentl canfirmation of is ideas He used Tanatosian, nat called the Fblien Hamma, ‘shich interactions between loetons and phonons ae Jcluded but Ceulomp intractensaromifed excest as bey’ cm be included inthe enezges ofthe individual flecross and phonons, Froalien used a perarstion theory approach an fouud iusisbility ut dhe Pets Surface the. clacton pronon inferaetion were Sufciemy strong, Herbert Iblieh realized thatthe ‘bservation that-goed conductors (capper, gold) tend hot to Geoome sirereundacior might ean that fnperconduetvity is proctied hy 4 relatively some, inferation between the conduction elections and the Tntice vitrtions, or honons, in those metals thx were not goed nontal conductors, “The nent big experimental discovery wps dane by 10 groups: Goodin, who was making thermal tonduetivity experimen, and Brown, Zemansky ard [Doorse, who were making spee:ficheatmeasuremens. They dcuvered wll isealed liceosrey gap. T % 7 Figs. Temperature veraon of elesronie spite heat of onal tl eestor “The specific Heat af w solid C, vat be expresses = YE tay whote the frst tem is the electron ‘dntrdution (predominant for poo! meals at very foe feruperture) an the sce tennis. the. La Contribution, The graph hove ft shows the savior ‘of none? mil vile tha ia the right shows ‘behavior inthe superconducting sae. The saris featurcorthe cura thar below Ts the false 982 indicating 9 cleat gap in the. slecrtnie. enemy speculum Tie possible nen eves for elecvas ree {w move. about a. volume. V_are found om, the Sehvingerecuation. Theeacmy levels are quantize find each level (2) ean be peer psd by twa “ermions ‘ane th spin up ane one with spin dwn. ACT 0. the fnorgy leve's Will be copletely Billed up wo a cenain ‘is whe is called she Fermi eneseysc,-AtT ~0, thon willbe tonceupiedstatorvith ea, Inmetalsin ‘aval sate, eleettens move above the Ferms kneray INT 0K. Hutin speroordeetingstete tht ienot ey you ond to impat sufficiently more euensy fxevenme an enerey gan ahove the Fermi Fnerey. ‘yas a sial clue towards cmccing. the theory oF superconductris ‘Thos dy 1959-56, t90 inications were clear the leetton phonon interseion and energy gap. Ll fumpteheusive theory was sill euging seienssts Memhile, Schatroth showed that stat ne with the Frallieh THamilonicn, sone earnet decive the Messner eTect in any order of perturbation theory Rassien poste” Migdalsthoory supposedly eorect {terns oforder mM)" gave no papa nsf at the Temi surlace aad no Indication of -Wob Sebuioter suramarizo she situation as “This was he state of ow tndvstandng of the etectodsaamtes (felsic eyecare mss 98a ters Satisfactory phenomenaloay, Ino “explanation” on Intervccepie terms. What was the rare of the Impertondioting siake hat made i have these remarkasleproperies? This question was antiered by ‘ne sake by the lassie piper of Randeon, Cope ona Sehrietiee (1957). Events Leading to the BCS Theory The ann whos pat breaking esc eatin Satisfactory explanation tw the. pasnonsenon of Supotconduetivity was John Bardeen. Burdasn reals that "My fest inmoduetion 10 superconducthaty cane ihe 1930 and greatly potted fron reading Daal Shccnbere’s ite Bock on sapercometinty shih avons excellent summary ef he experimental ings dit of the phenntonoligical theries Oat foal Deen flevefoped* Radcen's fist abortive “atempt t *P. pagation Alf Senos Conmaication 49 onsruta theory, 940, was stonglyintaenved by Londons ideas an the key ices was sal mre 2a athe Femi surface ariing. om smal lihice Fixplaeren's. However this Wek eas inemapsec By several yeursofwsrtime research, al then tee wt Hacdeen joined the wroup at the Tell “Tlephone Laboratoses hers his wore tured fe semicon tors ardeen cane o University of Minos at Urhanain the early T9593 as jointly a professor of physics and ¢ profesor of elstineal engiteermg at ‘he fom Bell Ltbmatores waere ho, Walter rata, aad Wa Shockley uneated he ansistorfewae not unl the as a resul of the discovery o” te tsotope ell tha Eandeen aguin hogan to. eccnieiterested th Sipsreonducivine Haneen teard aout the isotope effect invarly Nx, 1980 in telephone ell fem Seen fd realized that the jcotose effect identified the lnteratot beeen clectres and phos thet mst be response fr the henocrenon. The basic ea wr beu Fenmi degenerare gas oF neuly foe electrons wil a sakly attactiv> interaction by way of the atioe Ponons, he atreed fo wevive his ead tory of nergy gaps atthe Fermi surluce, wth the aps Row atising four dsnamie Interactions with the phonons father thax ifom sill sate lance cispagemetts Baricen wed a variational metal tier than peturbacionappragch but tae thcory ay alse based et the elvtnn sel-cnenpy in ho fit of ponooy Al he same tine, Bardeen rad Frohlich tndependenty put fvand theories of superuomcrvity whieh late on treats nso cams cident at ey allofth selFenergy is included inthe sural state ne! isbinle changed inthe wansiti. A theory aaving trie many-body mteraetion herween he clecttens seeredi0 2 eyuired to aeeuene Ft superent Ay Howovs., sah oF thew sad they thought an essential Postion of he problem Tal wo coat what happened 12 tho eleticons whose energy was wal to the Fett fang. The interaction sided by’ Fright af Fist Sich quite spacalis be ne both novel and pont involving tte right dependence on the iotapie mun ‘Phere wos however a ngjor ratte in anderstandiag fw it could play a role, since the baie Cavlarnb ineraction between electrons s both fepulive and very mack stronger, “AS Lande pur i've ron repeat! Couonstav In 195, stituted by writing a review antile om the stu the theory of superconducivity, Jam Boren sided to renew the alla om the pioblem, Solving ltarprolemprovedtobe dificult tisk There wa he the sr af power competition, Richard Fey nts, tne ofthe masters of quinn sletredynamics, an fenowned Soviet Physivists like Landa and ego yubor were close ta th solution. In quantum jerbdynamiss clecuons in vacua interact With one ‘other via photons, or qaumtizd light weaves, fa the Proce! Bardeen ws cy-nu tool, ¢ etronsin meals interact with ome arother via phedees, ur guantized lewive vibsations, This seas the problem which Soli Bardeen and David Pines, his postdoc fellow a the University of Illinois during the peti 1959: stacked, What they fosnd fy extending an appre ‘whieh David Bahn ane. David Pines had carlice developed or understasling the cor sequences oF rox-clectrom interactions in rita, ras that he meclunn is the messege, When “hey tous into account the influence of electronic sereering processes on at tlectromelectrun and election ineraetien, the Feud thatthe presence of a second commer the makes possible’ a net attractive. interact on hapa of elostons whe energy eilerence 1 than acharcctvistc phonon snerey Fig 9 Baier (let, Cooper (enter) and Scher In 1955, when Pines tefl University of Enis, Brdden decided dat reinforce ets vere needed I called up CN. Yang at the Testute for Advenced smdy a Princeton, to ask for 2 posidae vers i he Field theory. Vane reromsmended sun Cooper snes Cooper's fickground was 1 pasiele physiet Cooper has recently completed hisPhD in garicle physvs in the process he ad leamed set of mathematical lechniquescalled quantum “eldtheory. He wasted fasone ofthe best young sen inthe subject. Bande Fete migit be imporantw knovr these ‘echn ques in order tickle the problem af superoonductiy. So ie a Fig, 10, Sehemasic repesentaion of Comper Pa 50 wited Couper to come w Urbana, Because of is ssery in quantum mechanics Ke was jekingly called by otters in the depertneat as “Bardeen quantune imeckanie". Meanwhile, Bob Schrier was tthe University of Hinois a6 a graduate studeat, He had er henna states at MIT, woking ina group of sai state physicists When he reas tradition time. he deciced ty work with Ranieen Initislly, Rardesn supgested “scma. ware on scininviustrs When came time tiv 2 resis, ier chase to woek an superenndietivity The team was astomnbled at the University nf Hlinsis phhyses depanmiont, Banteen and Caper hc za shane naffice Intherrcantime, Schrieffer wankesinaroam fl of exher grants stadonts The stution was aot conducive, butspiritofteteiowas on high + son howame els that snes the existing field thooretie methods were hasce on perturbation tsar, snoter seme woul ae t be devsed. Breen Stressed the importance of an ene-gy” gp the fexeitatin spectrum and thar suporeondtetiviy cle ‘0 eandensatin in momentum space af 4 coherent ‘Superposition oF narmal-sate configurations. But It ‘as ficult ro explain quantiatively. Farunstely, Tanda's ‘hony of a Fett liquid) voviled jeeessary, basis Ter" Geating the normal-state xciations in onc-le-one eomtspondenee with “he ites electyn gas 0 that he small condensation energy hoswoon thesuperand norinal phases could he slate The fist, major beeakshcough this tio made. in superwancductiviy came fom Leen Coaper. Coopet ‘vas making an efor fo find out why’ thero was an agation A varal f Stines Commectin ‘enerey gap. Cooper studied the genera theories of ‘Guat ‘tiechanies and considered simpliticd adel ates interactions of ewoctcctznns At very fa ‘emperatore, ll sates upto Fermi level ar filled snd hanes. no available th these clecrons. He. then {Seaminad what considersd = the fis sis that the ‘Coutsmb repulsion of elevtrans, because they are of the same shure, The second was thi the electrons interact ia lattice vibrations: one eleston displaces 3 hielsis ar i pastes by tho maolous which sn hin [tracts another electron forming a pair of moving Glectons, Ihe interaction Was energetically forse “thers was net atracion, Cooper sonluded that supercondactvny arose when theetiveinemeton of neler ferns other Trorgh the ates, wa lange ta tse ied epulsion This then hocume a “ererion tor Sipercemeliiy Cone pablsiels pape in 1956 finds une othe famou papers Ihe history ob ipesconductiviy The incerasting pas cf elects ihave since been known ax "Cooper air er the Ginooverr. es imorosing to ote thts is 198 papa Canpsrretored to Citabury and Seater a+ Enbing thao electrons or even mis, omnes together andl zero or ttegal spin ould bebe IikeBosons this point Bardeen, Cooper and Sehr decides to lay > gensalize Coopers tsils {0 many elsctor Sens The ouble wes that a Cooper Pair pease Uo crt wilh hil Rua lscow waft ‘They ndertoad th sivele Cooper ir No usgble The break came. when sb. Sclrieer Succeeded in guesing the natire of te ston ak sects aor ‘Tey them stenpted la generalize te Salons the higher temperatres and shew thst Fens ‘cold neu rll of the et Sperconevctiity, The ftv! jeint-piper of he rupwas published ia Febauay, 1957 Mis was the prolif ratory The tio then fle they were close fo the success Bat they st had fais Berdcen none to Stckhaies n tollest bis 1986. Nobel Pave while Cocper and Scnricnor ongrosced ints. deep thineing and faleulaon, Tut wilsia few malts they” were Successful. Te became leer that ths "Roy 10 Supercunductviy isthe vandessaliva of all eletuon pales inga-montehgunt speed, hat Is they will have me moraenton {though thoy’ may be pyseal Tar Spatt) anda be described by ering e wars hac Tis easy to understand thet such situation nay arse asthe Cooper Pairsare Bosors andar not stricted be Paull Exclusion Prinepie wo oecupy same enerzy 2 3 2 2 a