Effects of pressure on the superconducting properties of magnesium diboride.pdf

Effects of pressure on the superconducting properties of magnesium diboride X. J. Chen, H. Zhang, and H.-U. Habermeier Max-Planck-Institut f¨ur Festk¨orperforschung, D-70569 Stuttgart, Germany (Dated: Received 21 May 2001) 2 We discuss the effects of hydrostatic pressure on the superconducting properties of MgB2 within 0 the framework of Eliashberg theory. By considering the pressure dependences of all parameters 0 appearing in the McMillan formula, we show that the calculated pressure derivative of Tc as well as 2 the variation of Tc with pressure are in good agreement with recent measurements. The pressure r dependences of the energy gap ∆0 , the effective interaction strength N (EF )v , the critical magnetic field H (0), and the electronic specific heat coefficient γ are also predicted for this system. A a c M comparison of pressure effect in non-transition elements clearly suggests that MgB2 is an electron- phonon mediated superconductor. 8 PACS numbers: 74.62.Fj, 74.70.Ad ] n o I. INTRODUCTION groups observed a decrease of Tc with increasing pressure, c with initial pressure derivative dT /dP of –0.8 K/GPa - c r The recent discovery of superconductivity in MgB2 (Ref. 15) or –1.6 K/GPa (Ref. 16),