Müller, Karl-Alexander

Karl Alexander Müller, rojen 20. aprila 1927 v Baslu v Švici. L. 1987 je z Georgom Bednorzom prejel Nobelovo nagrado za fiziko za delo na superprevodnosti v keramičnih materialih.
K. A. Müller je doktoriral je iz fizike na Tehniški visoki šoli v Zürichu 1958. Zatem je bil pet let vodja skupine za magnetno resonanco v institutu Batelle v Genevi in ob tem predavatelj na Univerzi Zürich, pozneje pa vodja oddelka za fiziko v raziskovalnem laboratoriju IBM Zürich v Rüschlikonu, kjer je ostal do upokojitve. L. 1962 je bil izvoljen za docenta, 1972 pa za rednega profesorja na Univerzi v Zürichu. Professor K. A. Müller je objavil več kot 250 znanstvenih del s področja paramagnetne resonance in strukturnih faznih prehodov. Njegova dela so utrla nova pota za določanje statičnih in dinamičnih kritičnih eksponentov in bistveno pripomogla k uveljavitvi elektronske paramagnetne resonance kot metode za določanje dinamike in strukture trdnih snovi. Med drugim je raziskoval lastnosti kvantnih paramagnetikov n.pr. stroncijevega titanata in sorodnih feroelektričnih perovskitov.
L. 1980 je začel z raziskavami snovi, ki bi utegnile postati superprevodne pri višjih temperaturah. V tem času je bila najvišja znana kritična temperatura Tc=23 K v Nb3Ge. S sodelavcem G. Bednorzom mu je 1986 uspelo doseči superprevodnost v lantanovem barijevem bakrovem oksidu (LBCO) pri temperaturi 35 K. To senzacionalno odkritje je takoj povzročilo intenzivne raziskave visokotemperaturnih superprevodnikov po vsem svetu, predvsem na sorodnih oksidih, pri katerih sta lantan in barij zamenjana s sorodnimi elementi. Njuno odkritje sta kmalu potrdila S. Tanaka z Univerze v Tokiu in P. Chu iz Houstona. V nekaj mesecih je Chu dosegel temperaturo 93 K, približno leto pozneje pa so na Japonskem uspeli izdelati snov s Tc=107 K. Ob tem so se pojavila pričakovanja, da bi na osnovi odkritja profesorja Müllerja lahko sintetizirali superprevodnike, ki bi delovali pri sobni temperaturi. Medtem ko je bil pojav superprevodnosti do leta 1986 omejen na izredno nizke temperature in je zahteval hlajenje s tekočim helijem, delujejo novo odkriti materiali pri dovolj visokih temperaturah, da jih moremo hladiti s tekočim dušikom, kar je izjemnega pomena za razvoj elektrotehnike in elektronike. Müller in Bednorz sta za odkritje visokotemperaturne superpevodnosti prejela Nobelovo nagrado za fiziko že jeseni 1987, kar je najkrajši rok med odkritjem in nagrado v zgodovini Nobelove fundacije.
Profesor K. A. Müller je prejel še celo vrsto drugih nagrad in priznanj. Med drugim je zunanji član ameriške National Academy of Sciences in častni doktor enajstih uglednih univerz.
Profesor K. A. sodeluje z eksperimentalnimi skupinami v Ljubljana že od 1965. Njegov laboratorij v Zürichu je bil vedno odprt za mlade raziskovalce iz Slovenije, ki jim je s svojim izjemnim znanjem večkrat pomagal pri izvedbi eksperimentov. Udeležil se je več kot desetih konferenc in mednarodnih letnih šol v nekdanji Jugoslaviji, ki jih je organiziral akad. Robert Blinc s sodelavci, med drugim tudi simpozija za fiziko trdnih snovi v Porotorožu ter znanstvenega srečanja na Bledu. Večkrat je tudi predaval na Institutu Jožef Stefan (IJS) in na SAZU v Ljubljani. S skupino za kompleksne snovi na IJS, ki jo vodi prof. Dragan Mihailović, še vedno sodeluje pri raziskavah mehanizma visokotemperaturne superprevodnosti.
Skupščina SAZU je K. A. Müllerja dne 23. aprila 1987 izvolila za dopisnega člana.

(april 2012)

Karl Alexander Müller
Born 20 April 1927 in Basel, Switzerland. In 1987 he was awarded together with Georg Bednorz the Nobel Prize in Physics for their work in superconductivity in ceramic materials.
K. A. Müller received his Ph.D. from the Swiss Federal Institute of Technology (ETH) in 1985. He then joined the Batelle Institute in Geneva as manager of the magnetic resonance group and lectured at the University of Zürich. Later he accepted a position at the IBM Zürich Research Laboratory in Rüschlikon, where he remained until his retirement. In 1967 he was elected a Professor of Physics at the University of Zürich. Professor Müller published more than 200 scientific papers in the field of paramagnetic resonance and structural phase transitions. His work opened the way toward measuring static and dynamic critical exponents and promoted paramagnetic resonance as a useful tool for the study of dynamics and structure of solids. Among other problems, he investigated the properties of quantum paramagnets such as strontium titanate and the related ferroelectric perovskites.
From 1980 on, he started a search for substances that could become superconducting at higher temperatures. At that time, the highest known critical temperature was Tc =23 K in Nb3Ge. In 1986, together with his coworker G. Bednorz he was able to reach superconductivity in lanthanum barium copper oxide (LBCO) at a temperature of 35 K. This sensational discovery immediately triggered intensive research on high temperature superconductors all over the world, focusing primarily on oxides where lanthanum and barium are substituted by similar elements. His discovery was soon confirmed by S. Tanaka from Tokyo University and P. Chu from Houston. In a few months, Chu achieved a temperature of 93 K, and roughly a year later a substance with Tc =107 K had been prepared in Japan. Expectations were raised that in the wake of the discovery by Prof. Müller it might become possible to synthesize superconductors which would function at room temperature. Before 1968, the phenomenon of superconductivity had been restrained to extremely low temperatures thus requiring a cooling with liquid helium, whereas the newly discovered materials are operational at sufficiently high temperatures to allow cooling by liquid nitrogen. This has had extraordinary implications for the development of electrical engineering and electronics. Müller and Bednorz received the Nobel Prize for the discovery of high temperature superconductivity already in 1987—the shortest time on record between the discovery and the prize.
Professor K. A. Müller received many other prizes and recognitions. He is a foreign member of the US National Academy of Sciences and honorary doctor of some 11 universities.
Professor K. A. Müller has been collaborating with the experimental groups in Ljubljana from 1965 onward. His laboratory in Zürich was always open to young researchers from Slovenia, who were guided by his exceptional knowledge and experience. He took part in a number of conferences and international summer schools in former Yugoslavia, organized by Academician Robert Blinc and his coworkers, for example, in a physics symposium in Portorož and scientific meetings at Bled. On several occasions he presented colloquium talks at the Jožef Stefan Institute (JSI) and SASA in Ljubljana. He is currently collaborating with the research group for complex materials, led by Professor Dragan Mihailović at JSI, on investigations of the mechanism of high temperature superconductivity.
The Assembly of SASA elected Professor K. A. Müller on 23 April 1987 a corresponding member of SASA.

(April 2012)