Physicist.

Lev Davidovich Landau (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, and the two-component theory of neutrinos. 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).

Source:

1.) Henry F. Schaefer (2003). Science and Christianity: Conflict Or Coherence?. The Apollos Trust. p. 9. ISBN 9780974297507. "I present here two examples of notable atheists. The first is Lev Landau, the most brilliant Soviet physicist of the twentieth century."