High-pressure effects in anti-post-perovskite superconductors V3 Pn N _x (Pn = P, As)

Pressure effects on the superconductors V3PnNx (Pn = P and As) with the two-dimensional anti-post-perovskite structure were investigated. It was found that with increasing pressure, the superconducting transition temperature (Tc) decreases with a negative differential pressure (P) coefficient dTc/dP = -0.19 and -0.013 K/GPa for Pn = P and As, respectively. This is in marked contrast to the positive differential pressure coefficients reported for other vanadium-based superconductors with a three-dimensional crystal structure. The observed change in Tc under pressure is revealed to be closely correlated with the evolution of the normal-state resistivity. The results support the phonon-mediated superconductivity in V3PnNx.