Pressure dependence of superconducting transition temperature of MgB₂ up to 8 GPa

Abstract

The pressure dependence of electronic structure, phonon frequencies, electron -phonon coupling constant, and the superconducting transition temperature T c in MgB 2 are calculated via zone-center frozen phonon modes calculations using the FP-LAPW method. The calculations are performed from pressure dependent lattice parameters measured experimentally up to 8 GPa. Under quasi-hydrostatic pressure, T c is found to decrease with an approximately quadratic dependence, deviating significantly from the linearity. It is shown that the pressure-induced anisotropic change of lattice parameters, the increasing E 2g phonon frequency, and nonlinear electron -phonon coupling are three key factors of producing nonlinear T c (P) observed in MgB 2 .

Superconductivity of MgB2in the BCS framework with emphasis on extrinsic effects on critical temperature

“…The dominant contribution to the decrease of T C under pressure has been proposed due to an increase in phonon frequency and decrease in coupling between phonons and charge carriers [123][124][125]. The Raman spectrum of MgB 2 shows a large positive shift in the frequency of the E 2g mode under pressure [117,126,127], in support of the theoretical arguments.…”