Lev Davidovich Landau ( Russian: Ле́в Дави́дович Ланда́у; IPA: [lʲɛv dɐ'vidəvʲit͡ɕ lɐn'daʊ]; January 22 [O.S. January 9] 1908 – April 1, 1968) was a prominent Soviet physicist who made fundamental contributions to many areas of theoretical physics. His accomplishments include the independent co-discovery of the density matrix method in quantum mechanics (alongside John von Neumann ), the quantum mechanical theory of diamagnetism, the theory of superfluidity, the theory of second-order phase transitions, the Ginzburg–Landau theory of superconductivity, the theory of Fermi liquid, the explanation of Landau damping in plasma physics, the Landau pole in quantum electrodynamics, the two-component theory of neutrinos, and Landau's equations for S matrix singularities. He received the 1962 Nobel Prize in Physics for his development of a mathematical theory of superfluidity that accounts for the properties of liquid helium II at a temperature below 2.17 K ( −270.98 °C ).