Number 217 (Story #1), March 10, 1995 by Phillip F. Schewe and Ben Stein HIGHER CURRENT DENSITIES can now be achieved in high-temperature superconductors. Arunava Gupta and his colleagues at IBM (Yorktown Heights, NY) have measured current densities as high as 10**5 amps/sq cm in mercury-cuprate (Hg-Ba-Ca-Cu-O) films at a temperature of 110 K. This is ten times the density achieved with thallium or bismuth-based superconducting films at such an elevated temperature. These measurements were made with a magnetic field perpendicular to the film sample. When the field lines are oriented in the plane of the film, an even higher current density, 10**7 to 10**8 amp/sq cm, can be sustained without the film losing its superconducting property. Gupta's samples can bear the high currents only in low perpendicular magnetic fields (high fields would disrupt the superconducting state), but this would still make the mercury-based compound potentially valuable in such applications as microwave transmitters and filters, or in the fabrication of superconducting quantum interference devices (SQUIDs), which are highly sensitive magnetometers. (L. Krusin-Elbaum, C.C. Tsuei, and A. Gupta, Nature, 23 February 1995.)