Pressure Effect on the Charge-Density Waves and the Superconductivity in NbSe₃

Abstract

The pressure effect on the CDW formation and the superconductivity in NbSe 3 is investigated up to 18 kbar by resistive and diamagnetic measurements. Both the T 1 -CDW and the T 2 -CDW are suppressed under pressure, as reported earlier. The superconductivity appears at pressures above P c =7.5 kbar where the T 2 -CDW is suppressed totally. It was confirmed that the superconducting transition temperature T c exhibits the maximum value just above P c while it decreases gradually at higher pressures. It was found that the initial slope of ln T 2 and the slope of ln T c above 9.5 kbar are almost the same. The results are discussed in terms of both collapse of the nesting of the Fermi surfaces and reduction of a dimensionless electron-phonon coupling constant under pressure.