Absence of a structural transition up to 40 Gpa in MgB2 and the relevance of magnesium non-stoichiometry

Abstract

We report measurements on MgB2 up to ~40GPa. Increasing pressure yields a monotonous decrease of the lattice parameters and of the c/a ratio, but no structural transition down to parameters smaller than those of AlB2. The transition superconducting temperature also decreases with temperature in a sample dependent way. The results are explained by an increase of the filling of the 2D pxy bands with pressure, the Mg stoichiometry determining the starting position of the Fermi level. Our measurements indicate that these hole bands are the relevant ones for superconductivity.

arXiv commentsubmitted March 9th 2001, PRB accepted

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• Dependence of the superconducting transition temperature of single- and polycrystalline MgB2 on hydrostatic pressure
• Crystal growth and characterization of MgB2: Relation between structure and superconducting properties
• Disorder induced collapse of the electron phonon coupling in MgB${}_2$ observed by Raman Spectroscopy
• Raman spectra of MgB2 at high pressure and topological electronic transition
• Possible superlattice formation in high-temperature treated carbonaceous MgB2 at elevated pressure
• Heat capacity of mesoscopically disordered superconductors:implications to MgB${}_2$
• Pressure Effects and Large Polarons in Layered MgB_2 Superconductor