03 January 1992
Vol 255, Issue 5040

About The Cover

The calculated surfaces in momentum space (``Fermi surfaces'') for the charge carriers in the high-temperature superconductor YBa2Cu3O7. Charge carriers can be electron-like or hole-like; blue indicates low-velocity, high-mass carriers, and red indicates high-velocity, low-mass carriers. This Fermi surface, first calculated theoretically, has recently been confirmed by several experimental spectroscopies. See page 46. [Image by R. E. Cohen with AVS 3.0 software; image printed on a Kodak XL7700 at the Naval Research Laboratory Connection Machine Facility]