Obituary of Yuri Bychkov (1934-2012)

Yuri Arkadievich Bychkov passed away after an extensive cancer surgery on 30 December, 2012, in Moscow (Russia). Yuri was an outstanding member of the Russian school of theoretical physics founded by Lev Landau, and is internationally known for his remarkable contributions to the various branches of condensed matter theory.

Yuri was born in Orenburg, south off the Ural Mountains, on 24 May 1934. He was from the generation of the Russian people whose adolescence fell during the years of WWII. His father perished in battles for his homeland. His mother also died rather early. Yuri revealed early independence having graduated from high school one year ahead of his classmates. “It was boring for me there”, he remembered. In 1951 Yuri entered the Moscow Institute for Physics and Technology (known as MFTI), the Institution with the highest level of physics education in physics in the USSR and the highest requirements for the students. There he developed strong interests in theoretical and mathematical physics and graduated in 1957 completing a paper on mesodynamics under the supervision of Vladimir Berestetskii, a founder of the Chair of theoretical physics in MFTI. In the same year, Yuri passed the exams of the legendary Landau’ Theoretical Minimum and was accepted for graduate study to his division in the Kapitza’ Institute for Physical Problems in Moscow.

This period was remarkable for fast penetration of field theoretical methods into the statistical and condensed mater physics, and the Landau group was on the forefront of this development. Yuri advanced the theory of thermodynamic and galvanomagnetic phenomena in strong magnetic fields. In particular, he unveiled the connection between the analytical properties of the electron scattering amplitude in strong magnetic fields and the Dingle factor controlling amplitudes of the oscillatory phenomena.

In 1965, after establishing the Landau Institute for Theoretical Physics, Yuri moved to this Institute and became its first Scientific Secretary. At the same time he became interested in the properties of one-dimensional systems. His most influential paper of this period (1966), written in collaboration with Lev Gor’kov and Igor Dzyaloshinskii, proved the possibility of the superconductivity of monovalent one-dimensional metals. In such a system the superconductor instability interferes with the Peierls instability doubling of the lattice period. As a result, the quasiparticles are four-particle electron-hole excitations, and the theory is formulated in terms of “parquet” diagrams becoming more sophisticated than the standard BCS theory.

Gradually, Yuri’s interests shifted in the direction of two-dimensional (2D) electron gas in semiconductor heterostructures. In his 1981 paper (with Sergey Iordanskii and one of us, GME), Yuri developed a theory of few-electron complexes in a strong magnetic field, especially a theory of charge and spin excitons. The paper became instrumental for experimental studies and later Yuri regularly returned to this problem generalizing the model, in particular, developing a theory of biexcitons, and collaborating with experimenters both in Russia and abroad.

In two influential 1984 papers (with the other of us, EIR) Yuri applied a theory of spin-orbit coupling developed previously for uniaxial three-dimensional systems to 2D electron gas. This resulted in introducing into the Hamiltonian a new term that is currently known as a Bychkov-Rashba term. The importance of this term for physics of low-dimensional systems and applications is based on the fact that in them spin-orbit coupling can be controlled by applying an electric field. In particular, this term is in the heart of the proposal of the spin transistor that became a paradigmatic spintronic device and is widely invoked in the current search for Majorana fermions in solids.

After the fall off the Iron Curtain, a wider world opened for Yuri. He established new fruitful scientific collaborations, especially in Germany (Braunschweig) and France (Grenoble). In 1990s, the efforts of the collaboration were mostly focused on topological excitations in 2D systems. Among the most interesting results is analytical derivation (in 1997) of the Skyrmion Lagrangian, including the topological Hopf term, from a microscopic Hamiltonian by expansion in a small Lande factor. For Yuri, his scientific work has always been closely related to his teaching. Therefore, besides the more traditional theoretical disciplines, Yuri started lecturing topology and prepared a manual “Topology for Physicists” for students of MFTI.

Yuri was an intelligent, friendly, and charming person. His hospitable home in Chernogolovka (near Moscow) where he lived with his wife Rimma was always open for friends and colleagues who found comfort and warm reception there. The community will badly miss Yuri.

Alexei A. Abrikosov

Argonne National Laboratory, Argonne

Guerasim M. Eliashberg

L. D. Landau Institute for Theoretical Physics, Chernogolovka

Emmanuel I. Rashba

Harvard University, Cambridge