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.

To commemorate him and his contributions, O. V. Lounasmaa -laboratory organized a Kopnin Symposium on 24 Jan, 2014.

Nikolai Kopnin had been a frequent visitor of the Low Temperature Laboratory for several years until in 2000 he became a member of the staff. His early collaboration with the Laboratory was concerned with the dynamics of quantized vortices in helium-3 superfluids. Lately he contributed extensively with his studies to the development of superconducting nanoelectronics to the new backbone of the Laboratory's research.

Nikolai Kopnin 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) on his work on the 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 works have been highly recognized and he was one of the leading experts in this field world-wide, 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, he developed the microscopic theories for dissipative and non-stationary flow in Fermi superfluids, in particular in superfluid 3He, he worked on a 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.

By extending his theory of the "Kopnin force" to chiral superfluids Kopnin already in 1991 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 under intensive search in solid-state materials. According to the recent works by Kopnin, 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, who consider him a noble man with a strong passion to 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, he always found his way to interesting hikes and travels to wilderness places. 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.