Paper detail

Physics of $π$-Meson Condensation and High Temperature Cuprate Superconductors

The idea of condensation of the Goldstone $π$-meson field in nuclear matter had been put forward a long time ago. However, it was established that the normal nuclear density is too low, it is not sufficient to condensate $π$-mesons. This is why the $π$-condensation has never been observed. Recent experimental and theoretical studies of high temperature cuprate superconductors have revealed condensation of Goldstone magnons, the effect fully analogous to the $π$-condensation. The magnon condensation has been observed. It is clear now that quantum fluctuations play a crucial role in the condensation, in particular they drive a quantum phase transition that destroys the condensate at some density of fermions.