Lev Landau

Lev Davidovich Landau was born in Baku in 1908 and was a prodigy by any standard: he entered university at thirteen and had published on quantum mechanics before he was twenty. A Rockefeller Fellowship took him to Copenhagen in 1930, where he worked under Niels Bohr, whom he regarded for the rest of his life as his only teacher. He returned to the Soviet Union and by 1932 was head of theory at the Ukrainian Physico-Technical Institute in Kharkov, where he established the notorious 'theoretical minimum' — a sequence of examinations across all of theoretical physics that fewer than half a hundred people ever passed.

In 1937 he moved to Moscow, and in April 1938 he was arrested on a charge of comparing Stalinism to fascism in a leaflet. He spent a year in the Lubyanka prison and by his own account was close to death when Pyotr Kapitza wrote personally to Molotov and Stalin, staking his own standing on Landau's release and arguing that only Landau could explain Kapitza's newly discovered superfluidity. The gamble worked on both counts: Landau was freed in April 1939, and in 1941 he produced the theory of superfluidity that would win him the 1962 Nobel Prize.

His 1937 theory of phase transitions is his contribution to this branch, and it changed the subject's language. Instead of modelling a substance, Landau proposed writing the free energy as an expansion in an order parameter, keeping only terms permitted by symmetry. Minimising it reproduces a transition mechanically, and shows the ordered state breaking a symmetry the equations themselves possess. As a quantitative theory of critical exponents it is a mean-field theory and fails in three dimensions; as a framework it proved indispensable, extending through Ginzburg–Landau theory of superconductivity to the Higgs mechanism of particle physics.

With Evgeny Lifshitz he wrote the Course of Theoretical Physics, ten volumes covering the whole of the subject and still in use worldwide. In January 1962 he was catastrophically injured in a car crash on the road to Dubna; he survived, after Soviet physicists mobilised to fly in specialists and drugs from across Europe, but never did physics again. He received the Nobel Prize that year in a Moscow hospital, and died in 1968 from complications of the injuries.