Grigory Efimovich Volovik - 75
7 September 2021 marks the 75th anniversary of the outstanding scientist deputy-Editor-in-Chief of JETP Letters Grigorii Efimovich Volovik. Grigorii graduated from the Moscow Institute of Physics and Technology in 1970 and got his PhD in 1973. Since that time he works in Landau Institute for Theoretical Physics where he has defended the Doctor of Science degree in 1981. His works was honoured by Landau Prize of the Russian Academy of Sciences (1992), Simon Prize of the Institute of Physics, UK (2001), and Onsager Prize of the American Physical Society, USA (2014). He is a Member of the Finnish Academy of Sciences and Letters and of the German National Academy Leopoldina.
He made noticeable contributions to many areas of modern physics from the condensed matter to to the general relativity and elementary particle physics. His numerous contributions to many seminal achievements of ROTA project in the Low Temperature Laboratory in Otaniemy including the discovery of topological defects in superfluid phases of 3He are quite well known.
The other outstanding works of Gregorii are related to the theory of superconductivity.
First of all it is development of the theory of superconducting classes for nontrivial superconducting states made by Grigorii in collaboration with Lev Gor'kov.
There was established the correspondence between the symmetry of superconducting order parameter and type of zeros in the quasiparticle spectrum, as well as the corresponding low temperature specific heat behavior. The possibility of multi-component superconducting states possessing spontaneous magnetisation was pointed out. These conclusions have found numerous confirmations in many nonconventional superconducting materials including high Tc and heavy fermion compounds.
Another effect specific to superconductors with non-trivial pairing is the unusual magnetic field dependence of the density of states in the mixed state of type-II superconductors. Such type dependence called now ``Volovik effect'' serves as a fingerprint of nonconventional superconductivity, for instance, d-wave superconductivity in high Tc materials.
The natural continuation of studies of the order parameter structure in superfluid and superconducting phases and topological defects became the works devoted to the global topological properties of different superconducting states, collective (Higgs) modes in them and topological quantum Hall effect. The Grigorii's monograph ``The Universe in a Helium droplet'' became a reference book for new generation of condensed matter and field theory physicists.
Being the author of more than 450 scientific papers and two monographs Grigorii continues the active work.
All the staff of the journal, the Editorial Board, coauthors, and colleagues wish Grigorii Efimovich good health, and fruitful continuation of scientific activity.