Obituary of Alexander Alexandrov (1946-2012)

Sasha’s main focus was on superconductivity, especially the mechanisms of high-Tc superconductivity. He also worked on colossal magnetoresitance in manganites, molecular switches, memristors, etc.

Alexander Sergeevitch Alexandrov, a condensed matter theorist who was well known for his extensive contributions to the theory of superconductivity, physics of polarons, and other topics, died of a heart attack on August 14, 2012 in Campinas, Brazil.

Alexandrov was born on 30 July 1946. He graduated from high school in Novgorod, Russia and was admitted in Moscow Engineering Physics Institute (MEPhI) where from he graduated in 1970 cum laudae. He did his PhD thesis with Vladimir Elesin as his advisor on quantum transport in semiconductors in 1973. Soon thereafter he became interested in superconductivity, where he is well known for developing the bipolaron theory. His first highly cited work on bipolarons in superconductors was done with colleagues in Grenoble in 1980 during his yearly stay in France. As noted by Bednorz and Muller in their Nobel Address, these ideas inspired their successful search for high-Tc superconductivity in cuprates. After returning to Moscow, he continued to develop this approach with a small theory group at MEPhI. In 1984 Sasha got his second (Dr.Sci.) degree and soon became a Vice Rector of MEPhI.

Towards the end of the Soviet Union, Alexandrov moved as a guest scientist to Aachen, Germany hosted by Herbert Cappelman, where he published a few seminal papers on bipolaronic superconductivity and Kohn-Luttinger mechanism of superconductivity. In 1992 he moved to Cambridge, UK, as the first and only Mott Bye-Fellow at Gonville and Caius College where he started a very fruitful collaboration with Sir Nevill Mott and other scientists at the Interdisciplinary Research Center in Superconductivity, at the site of Cavendish Lab. During this period, together with Mott he published the pseudogap bipolaron theory and predicted a positive curvature of the upper critical field in bosonic superconductors. Very similar temperature dependences were measured in many high temperature superconductors, and experimental groups use his model for interpreting the data. In 1995 he moved to Loughborough University of Technology as professor and Chair of theoretical physics and later served as Head of Physics Department there.

Sasha’s main focus was on superconductivity, especially the mechanisms of high-Tc superconductivity, a still controversial topic. He was always a strong proponent of a decisive role of strong electron-phonon coupling (EPC) and the (bi)polaronic mechanism of high-Tc superconductivity. He constructed semi-phenomenological and microscopic models of bipolarons in HTSC that could give a clear insight into various data that are difficult to interpret using strongly correlated models without a strong EPC, e.g. an unconventional oxygen isotope effect, normal state pseudogap, specific heat systematics, and etc. His deep critical analysis of many popular models of superconductivity and strongly correlated systems have generated a lot of interest and very lively discussion in the community.

Sasha collaborated with many groups worldwide and kept in touch with his colleagues and former students. He never hesitated to take on new challenging topics that arose during his collaboration with, for instance, colleagues at Hewlett-Packard Laboratories (AB), where he frequently worked for extended periods of time, on topics like colossal magnetoresitance in manganites, molecular switches, memristors, etc., where he also obtained seminal results.

Alexandrov was an exceptionally productive researcher and an educator, as attested by his 7 books, three of them co-authored with Sir Nevill Mott, over 200 peer-reviewed papers published, including over two dozen Physical Review Letters. He powered ahead at full speed trying to cover as much ground as possible in his field. Sasha was very conscious that his time was limited, as he mentioned not once to his friends, so he pushed on. He has won a worldwide recognition as indicated by a large number of plenary and invited talks at international conferences, seminars and colloquia including the prestigious 1997 ‘Enrico Fermi’ lectures at the International School of Physics (Varenna, Italy) and the 2000 -'Mott Lecture’ (Florida State University, Tallahassee), this year’s ‘Mott Lecturer’ at CMD-24 of Europhysics Society in Edinburgh (nominated by JD), to mention just a few.

In addition to being a bright thinker and scientist, Sasha was a lively, approachable and very likeable person, not a frequent combination. With self-deprecating humor he’d discuss all kinds of odd adventures he got in, be it driving along German autobahns in an old Soviet-built car, or an unsuccessful fishing trip off the Pacific coast. He was always in good spirits, cheerful, and ready to help. He will be sorely missed by his family, friends, and colleagues.