Compressibility of the MgB2 Superconductor

Considerable excitement has been caused recently by the discovery that the binary boride system with stoichiometry MgB2 is superconducting at the remarkably high temperature of 39 K (1). This potentially opens the way to even higher Tc values in a new family of superconductors with unexpectedly simple composition and structure. The simplicity in the electronic and crystal structures could allow the understanding of the physics of high-Tc superconductivity without the presence of the multitude of complicated features, associated with the cuprates. Synchrotron X-ray diffraction was used to measure the isothermal compressibility of MgB2, revealing a stiff tightly-packed incompressible solid with only moderate bonding anisotropy between intra- and inter-layer directions. These results, combined with the pressure evolution of the superconducting transition temperature, Tc establish its relation to the B and Mg bonding distances over a broad range of values.