Florian Gebhard, Frithjof Anders, Jörg Fink, Ulrich Eckern, Roser Valenti at TUD, Chandra Varma at UC Riverside, USA, and Alex Braginski at Research Center Juelich, Germany
iW. Weber, Phys. Rev. B , 15, 4789 (1977).
Leo K. Kovalev, 1941 - 2014, Remembered
February 7, 2014 (PO26). On January 28, 2014, Prof. Leo K. Kovalev suddenly passed away in Moscow from a myocardial infarction at the age of 72. To the superconducting electro-machinery community, Leo K. Kovalev was well known worldwide through his work on electric machines with HTS bulk elements, comprising hysteresis motors, reluctance motors and motors utilizing permanent magnets. He also paid great attention to HTS-magnetic-suspension systems for high-speed rail-borne transportation and flywheels.
In 1964, he started his professional career at the Central Institute of Aircraft Engines, Moscow, after graduating from Moscow State Technical University Named After N. E. Bauman. A few years later he joined the Department of Electric Machines, the Dept. 310, of the Moscow Aviation Institute (MAI), headed by Prof. Albert I. Bertinov. During that time he pursued research in the field of MHD (magneto-hydrodynamic) energy conversion, and in 1972 he finished his Science Candidate (doctoral) dissertation on MHD generators. For the following ten years his research activity shifted to ionosphere radio physics, hydrodynamics and radio waves propagation at the Scientific Research Institute of Long-Haul Radio. During 1980-1982 he was the Deputy General Constructor of that institute. In 1982 he returned to the Dept.310 of MAI, headed at that time by Prof. Dmitry A. But, and continued research on MHD problems and in parallel extended his interest to low-temperature superconducting electric machines. When In 1986, when high-temperature superconductivity (HTS) was discovered, Leo concentrated his research on HTS electric machines and developed several series of cryogenic electric machines utilizing bulk HTS elements, operating at liquid nitrogen temperatures. He is the author of four books and more than 200 scientific and technical papers. In 1996 he attained his D.Sc. (habilitation equivalent) degree and became a Professor. Since 2002 he headed Dept. 310 of MAI, and in that same year he was awarded the State Prize of Russian Government in the field of Science and Technology. He initiated “The Centre of Superconducting Electric Machines and Devices” at MAI. Leo was an enthusiastic specialist in electromechanics, applied superconductivity, hydrodynamics and radio physics. He liked to first identify new scientific problems and then to solve them.
He actively took part in the international development of superconducting electric machines and was one of the initiators of the German-Russian cooperation, leading to the design and development of superconducting electric motors with liquid nitrogen cooling. The consortium comprised: Oswald Elektromotoren GmbH (Miltenberg), Stuttgart Technical University, IPHT (Jena), IFW (Dresden), Moscow Aviation Institute, A.A. Bochvar All-Russian Scientific Research Institute for Inorganic Materials (Moscow), All-Russian Electrotechnical Institute (Moscow), and the Institute for Solid State Physics (Chernogolovka, Moscow region).
Prof. Leo K. Kovalev was an Academician of the Russian Academy of Electrotechnical Sciences, an Honored Scientist of Russian Federation (RF), and an advisory council member of Highest Certifying Commission (RF).
Besides his research activities, Leo K. Kovalev was a true intellectual and a real friend for all his partners. Everyone who visited his Moscow home or countryside residence was surrounded with hospitality and warmth. He possessed a rare gift of charming his interlocutor from the very first words of communication. He left behind his dear wife Tatiana and a son, who like all of us will miss him very much.
Vladimir T. Penkin and Konstantin L. Kovalev
Alex Shikov Unexpectedly Passed Away
October 30, 2013 (PO22). Professor Alex Shikov unexpectedly passed away on October 26, 2013. Alexander Konstantinovich Shikov was born in Norilsk (then USSR) in 1948. He graduated from the Moscow Steel and Alloys Institute in 1971 and started his scientific career as a junior research associate at the Bochvar Institute of Inorganic Materials, also in 1971. He received his D.Sc. (Habilitation) degree in 1991. Since 1998, Dr. Shikov served as the deputy director of Bochvar Institute, and from March to August 2009 as its Head. He was then appointed as the Executive Director of Kurchatov Institute's center for Nano-Bio-Info-Cognitive (NBIC) Science and Technology. Memorial ceremonies were held on October 30, 2013, in Kurchatov Culture Center.
Shikov made an outstanding contribution to restoration of production of superconducting materials after the collapse of Soviet Union. Due to his scientific and management talents, Russian conductors for ITER are today competitive or even exceed the highest performance requirements. While at Kurchatov Institute, he directed research into superconducting materials for ITER and initiated production of HTS materials. Prof. Shikov was an author of three monographs, 250 papers in peer-reviewed scientific journals and 60 patents. He held a Chair of the Applied Superconductivity division in the Moscow Institute of Engineering Physics (Moscow’s outstanding Technical University).
Prof. Shikov was awarded several State Prizes in the field of science and engineering, an award of the Russian Academy of Sciences, the gold and silver medals of the International Exhibition of Inventions. He was a member of the Academy of Electro-technical Sciences of the Russian Federation. He also received an International Cryogenic Materials Conference Best Paper Award at the meeting in Tucson, Arizona in July 2009.
The memory about this outstanding man will be carried not only by his conductors with non-decaying currents and will last. All who knew him will remember his energy, motivation, optimism and achievements.
(Obituary based in part on that published in the Russian website “Superconductors in Power Industry”; see Superconductors in Power Industry, in Russian. Readers in Russian can find there some additional reading on and by Shikov.)
Nikolai Kopnin, Low-temperature Physicist
January 2, 2014 (PO25). Our friend and colleague Professor Nikolai Borisovich Kopnin passed away on October 20, 2013, during a lecturing trip to Rome. He was 67 years old.
Nikolai Kopnin had been a frequent visitor at the Aalto Low Temperature Laboratory1 for several years until in 2000 he became a member of the staff. His early collaboration with the Laboratory was on the dynamics of quantized vortices in helium-3 superfluids. Lately, his studies contributed extensively to the development of superconducting nanoelectronics, the new backbone of the Laboratory's research.
Nikolai received his physics education in Moscow. In 1973 he defended his PhD thesis on vortices in Type II superconductors under the supervision of Academician Lev P. Gor’kov in the Landau Institute of Theoretical Physics. He remained a researcher of the Landau Institute, and in 1984 he received his higher doctoral degree. In 2011, he was awarded the International Francis Simon Prize (together with his Landau colleague, S.V. Iordanskii). The Prize was for his work on forces acting on quantum vortices in superfluids and superconductors. One of these forces is now known as the "Kopnin force".
The main area of Nikolai Kopnin's research was superconductivity, primarily its non-equilibrium and non-stationary phenomena. His research work has been highly recognized and he was one of the leading experts in this field worldwide, as shown by the citations of his monograph “Nonequilibrium superconductivity" (Oxford University Press, 2001). He has contributed to the studies of anisotropic and layered superconductors, developed the microscopic theories for dissipative and non-stationary flow in Fermi superfluids, in particular in superfluid 3He, worked on new mechanisms for the formation of topological defects during rapid quench-cooled phase transitions, which has applications in cosmology, and he constructed theories of superfluid quantum turbulence. During more recent years he investigated the physics of mesoscopic structures and devices, including graphene. He published more than 150 highly cited articles in leading international journals.
Already in 1991, by extending his theory of the "Kopnin force" to chiral superfluids Nikolai predicted the existence of fermionic bound states, which have exactly zero energy. Today these quasiparticles are known as Majorana fermions - objects, which are still elusive in particle physics but may be observable in topological superfluids and superconductors. The bound states in chiral superfluids found by him have in addition the remarkable property that their spectrum is dispersionless. Now such flat bands are intensively searched for in solid-state materials. According to Nikolai’s recent work, the singular density of states in materials with a flat band may open the route to superconductivity at room temperature.
Nikolai Kopnin was a modest person who was always fair and considerate to his colleagues and friends, and they considered him a noble man with a strong passion for science. He was a person whom one could always trust and who dedicated and committed himself fully to his research activity. His free time Nikolai devoted to his family and enjoyed interesting hikes and journeys to wilderness. Those who were fortunate to be friends with Nikolai know that there is nothing better to look for.
Nikolai was always caring and loyal, with warm human spirits and intelligent sense of humor.
Matti Krusius, Jukka Pekola and Grigori Volovik
1Aalto University, School of Science, FI-00076 Aalto, Finland.
Jeffrey A. Stern Passed Away
October 11, 2013 (PO27). Dr. Jeffrey A. Stern was born on September 16, 1961, and passed away on October 11, 2013, at the age of 52, after a year-long battle with cancer.
Jeff received his B.S. physics degree from Rensselaer Polytechnic Institute in 1983 and his Ph.D. from California Institute of Technology in 1991. He spent his entire career at the Caltech Jet Propulsion Laboratory in Pasadena, CA. During his tenure at JPL, he made significant contributions to the development of superconducting sensors. He fabricated, tested, and space-qualified superconductor–insulator–superconductor (SIS) mixer chips, an enabling technology for band 5 (1140–1250 GHz) of the Heterodyne Instrument for the Far-Infrared (HIFI) on the Herschel Space Observatory. HIFI band 5 included some key spectral lines that have had a major impact on understanding of the interstellar medium (ISM) and astrochemistry. Possibly the most important is the ground state transition of hydrogen fluoride (HF). A large number of Herschel studies confirm that essentially all flourine in the diffuse ISM is in the form of hydrogen fluoride, HF. Consequently, this 1232 GHz transition, measured using band 5, can be an accurate tracer of the total column density of clouds. HF has been exploited in studies of the Milky Way and is now being used in observations of external galaxies. Also, Band 5 enabled detection of new species critical for understanding the production of water in the ISM such as H2O+, and made major contributions to unraveling the ortho-to-para ratio of the water molecule, giving strong indications about the conditions for the formation of water in space.
After delivering HIFI band 5 mixers, Jeff pioneered the use of phonon-cooled niobium nitride (NbN) mixers and fabrication of THz waveguide components using lithographic techniques. These technologies enabled new instrument concepts proposed for NASA's sub-orbital programs and follow-on space missions after HIFI. Concurrently with the THz mixer development, Jeff began work on new detectors for optical communications. Jeff was the first person in the US (2004) to make a functional superconducting nanowire single photon detector (SNSPD); the first person to fabricate a functional SNSPD in NbTiN (2006) and the first to fabricate arrays (4 to 16 pixels, 2005-2007). From 2012-2013, Jeff designed and fabricated fiber optic coupled SNSPDs from tungsten silicide (WSi) with the highest efficiency demonstrated to date (93%), 12-pixels arrays used in 2012 to establish an optical communications link with the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft orbiting the moon. His last accomplishment was a 64-pixel free space coupled SNSPD with an active area over 100 times greater than other state-of-the-art devices designed to be mounted on large telescope such as the 5 m Hale telescope at Palomar in California that can be used for optical communication with spacecraft around other planets, for observing ultrafast astrophysical events and for experimentally measuring quantum mechanical effects over large distances. Jeff Stern's innovations and technology leadership have led to a world-leading team at NASA developing optical detectors for space applications with near perfect efficiency, near zero noise, and high (sub-nanosecond) photon arrival timing resolution.
Outside of his profession, Jeff Stern was an avid participant in outdoor activities, including skiing, hiking, camping, rock climbing, swimming, scuba diving. He loved to cook and was a self-professed "foodie" who delighted in locating and trying new restaurants. He was also an avid gamer right up until the time he passed. Jeff was devoted to his family and is survived by Allison, his wife of 23 years, and his son Noah (19) and daughter Maddy (16).