Positron annihilation and high-temperature superconductivity

After a brief review of the theory of positron annihilation techniques and of experimental principles, we give examples of the successful determination of electron momentum density and Fermi surfaces in alkali metals, transition elements and compounds, and cerium. We then discuss the application of positrons in superconducting oxides. So far the best results have been obtained in YBa
2
Cu
3
O
7-x
, with confirmation of calculated band structure and observation of discontinuity at the Fermi energy.