Compressibility of the MgB2 superconductor - art. no. 012509

Considerable excitement has been caused recently by the discovery that, the binary-boride system with stoichiometry MgB2 is superconducting at the rem arkably high temperature of 39 K [J. Nagamatsu, N. Nakagawa, T. Muranaka, Y . Zenitani, and J. Akimitsu, Nature 410, 63 (2001)]. This potentially opens the way to even higher-T-c values in a new family of superconductors with unexpectedly simple composition and structure. The simplicity in the electr onic and crystal structures could allow the understanding of the physics of high-T-c superconductivity without the presence of the multitude of compli cated features, associated with the cuprates. Synchrotron x-ray diffraction was used to measure the isothermal compressibility of MgB2, revealing a st iff tightly packed incompressible solid with only moderate bonding anisotro py between intralayer and interlayer directions. These results, combined wi th the pressure evolution of the superconducting transition temperature, T- c, establish its relation to the B and Mg bonding distances over a broad ra nge of values.