- Person
- Lev Landau
- Lived
- 1908–1968
- Field
- Theoretical Physics
- From
- Soviet
The story
Superconductors carry electric current with no resistance at all when cooled below a critical temperature. The effect had been discovered in mercury in 1911, but by the late 1940s there was still no satisfactory theory of it. In the 1930s Lev Landau had developed a general theory of phase transitions, describing them through an 'order parameter' that is zero on one side of the transition and non-zero on the other.
In 1950 Landau and his colleague Vitaly Ginzburg, a Moscow-born Jewish physicist who later headed the theoretical department of the Lebedev Physical Institute, extended that framework to superconductors. They described the superconducting state by a complex order parameter, behaving much like a quantum wavefunction, whose size measures the local density of superconducting electrons. Writing the energy of the superconductor in terms of this quantity and the magnetic field, they could explain how superconductors respond to magnetic fields and to their own boundaries, without first knowing the microscopic mechanism.
In 1957 Landau's student Alexei Abrikosov used the theory to make a major discovery. In some materials, now called type-II superconductors, a strong magnetic field does not simply switch superconductivity off. It penetrates as a regular lattice of tiny whirlpools of current, each carrying exactly one quantum of magnetic flux. These are known as Abrikosov vortices. The Soviet physicist Lev Gor'kov, another member of Landau's circle, later showed that the Ginzburg-Landau equations follow from the microscopic BCS theory of superconductivity, giving every parameter a physical meaning.
In 2003 Ginzburg received a third of the Nobel Prize in Physics for developing the theory, and Abrikosov another third for his description of type-II superconductors using it. Landau, who had died in 1968, could not share the prize, but the theory still carries his name alongside Ginzburg's.
The theory remains in everyday use. Type-II superconductors, including the high-temperature cuprate materials, are described by Ginzburg-Landau-type models, and its mathematics has found echoes in quantum field theory and string theory.
Why it matters
Type-II superconductors, understood through this theory, make possible the powerful magnets in MRI scanners and particle accelerators.
About Lev Landau
Baku-born prodigy who founded the great Soviet school of theoretical physics, survived Stalin’s prison, explained superfluid helium and won the 1962 Nobel Prize.
More about Lev Landau
- Lev Landau predicted a strange way plasma waves fadeIn 1946 Lev Landau predicted that waves in a plasma can lose energy without any collisions, an effect confirmed experimentally in 1964 and now called Landau damping.
- Landau co-discovered the quantum density matrixIn the late 1920s, while still a teenager, Lev Landau independently introduced the density matrix, a basic tool of quantum physics, alongside John von Neumann.
- Lev Landau explained frictionless superfluid heliumLev Landau explained why liquid helium flows without friction below 2.17 K, introducing phonons and 'rotons'; it won him the 1962 Nobel Prize in Physics.
- Landau's Fermi liquid theory explains metalsIn 1956 Lev Landau introduced Fermi liquid theory, explaining why electrons in metals and atoms in liquid helium-3 behave almost like free particles.
- Landau levels underpin the quantum Hall effectIn 1930 Lev Landau showed that electrons in a magnetic field occupy discrete energy levels, now called Landau levels, key to explaining the quantum Hall effect.
- Landau and Lifshitz wrote physics' great textbook seriesWith his student Evgeny Lifshitz, Lev Landau began the ten-volume Course of Theoretical Physics, still used by graduate physics students worldwide.
- Landau's 'Theoretical Minimum' trained a generationLev Landau's famous 'Theoretical Minimum' exams, passed by only 43 candidates from 1934 to 1961, created the Soviet Union's greatest school of theoretical physics.
- Landau's theory explains how matter changes stateLev Landau's theory of second-order phase transitions introduced the 'order parameter', still a broad and powerful framework for how matter changes state.
Sources
- Ginzburg–Landau theory Wikipedia
- Lev Landau Wikipedia
- Abrikosov vortex Wikipedia
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