In Memory of Sergey Victorovich Iordanskii

Sergey Victorovich Iordanskii, a world-recognized physicist, Doctor of Sciences (phys.-math), Professor, Honored Scientist of the RF, passed away on June 14, 2020, in the 91th year of his life, after a heavy fight with corona-virus decease. In physics, Iordanskii is mostly known for his work on a force acting onto quantum vortices. In 2011, Iordanskii was awarded the Francis Simon Memorial Prize "For calculations and predictions of the fundamental forces acting on quantized vortices in superfluids, superconductors and other ordered systems". The Prize (together with his Landau Institute colleague, N.B. Kopnin) was awarded for the discovery of two kinds of forces acting on quantum vortices in addition to the Magnus force. One of these forces is named in literature the "Iordanskii force". Iordanskii derived this force in 1964-65. Much later, the fundamental topological origin of the Iordanskii force has been understood as one of the manifestations of the Aharonov-Bohm effect. Nowadays, this force has been recognized in cosmology as the one acting on spinning cosmic strings. S.V. Iordansky was born on 27/09/1929 in Orenburg. In 1956 he graduated from the Department of Physics and Technology of the Moscow State University. This Department was transformed into the Moscow Institute of Physics and Technology (MITP). Thus, Iordanskii was among the very first alumni of the MITP. In the early part of his scientific career, Iordanskii worked on problems of hydrodynamics under the supervision of his PhD advisor, the famous mathematician M.A. Lavrentyev. For his original work made in Sarov, Iordanskii was awarded the Order of the Red Banner of Labour (Orden Trudovogo Krasnogo Znameni). In 1956, soon after graduation, Iordanskii moved to the Steklov Institute of Mathematics.

In mid-sixties, scientific interests of S. V. Iordanskii shifted from classical hydrodynamics and plasma physics toward the low-temperature physics. After works about mutual friction between the normal and superfluid components in rotating Bose-liquid, he developed a theory for the rate of the vortex rings production due to the thermal fluctuations.

In 1967, in order to realize his desire to work in a more physics-oriented environment, Iordanskii joined the Institute for Theoretical Physics, now the Landau Institute. His first paper there gave an elegant solution of the problem of critical current of an accelerated particle when its motion is limited by emission of excitations. This work was continued together with his PhD student G.E. Volovik. In 1972-73, together with another PhD student, A. Finkel’stein, Iordanskii published pioneering papers on the quantum decay of a metastable state of a macroscopic system (the so-called problem of the “false vacuum”). They have found the instanton solutions describing the processes of quantum-tunneling decay of such states. Further on, in collaboration with L.P. Pitaevskii [JETP Lett. 27, 621, 1978], Iordanskii calculated the rate of a multiphonon decay of an elementary excitation in a Bose liquid near the sound line. The authors succeeded in finding a comprehensive non-perturbative solution of this problem.

In 1980, S.V. Iordanskii was invited to head the Theoretical Division of the Institute of Solid State Physics in Chernogolovka. His healthy-spirit character and sincere interest to physics made him very successful at this post. His solid mathematical background allowed S. V. Iordanskii to work with young colleagues on a broad spectrum of problems, from the growth of dendrites (with E. Brenner) to the drifting of Bloch lines in a ferromagnet (with V.I. Marchenko).

Iordanskii was deeply interested in the Quantum Hall Effect. In 1982 he proposed the semiclassical explanation of this effect. Together with his peer colleagues, Yu.A. Bychkov, G.M. Eliashberg, and E.I. Rashba, he developed a quantum-mechanical theory of two-dimensional electron systems in strong magnetic fields. One of his most cited work in the solid-state physics is about the spin-orbit interaction in heterostructures (co-authored with Yu.B. Lyanda-Geller, and G.E. Pikus [JETP Lett. 60, 206 (1994)] and subsequent publications). In the beginning of this century, Iordanskii made an original attempt to describe the Fractional Quantum Hall Effect (FQHE) in terms of the vortex lattices [JETP Lett.‏ 77, 247 (2003); 87, 581 (2008)]. Though it is still unclear how this daring work relates to the celebrated scheme of the composite fermions, all the principal properties of the FQHE have been reproduced by his theory.

Soon after coming to the Landau Institute, S.V. Iordanskii became an active member of the Chair for “Problems in theoretical physics” at Moscow Institute of Physics and Technology. During 1999-2003 years, S.V. Iordanskii headed this Chair. He was a successful PhD adviser. Besides already mentioned Finkel’stein and Volovik, he supervised Sergey Korshunov, V.V. Avilov, A.E. Koshelev, B. A Muzykantskii, and others.

Finally, it is worth to mention that S.V. Iordanskii very fruitfully collaborated with JETP Letters. As one of the most active authors, he published 37 papers in our journal. For about 15 years S.V. Iordanskii was a permanent member of the JETPL editorial board. His death is a great loss for his friends and colleagues and for all Russian science. The students and colleagues will never forget Sergey Iordanskii, outstanding personality and a devoted scientist.