Charge transport near pressure-induced antiferromagnetic quantum critical point in Magnéli-phase vanadium oxides

Resistivity (ρ) measurements on Magnéli phases V7O13 and V8O15 were performed under high pressures up to 3.5GPa. We have achieved a pressure-induced transition from an antiferromagnetic metal to a paramagnetic metal (PM) at critical pressures Pc≈3.4 and 3.3 GPa for V7O13 and V8O15, respectively. The critical behavior of ρ(T) near Pc turned out to be quite unusual in that no noticeable precursor effect was observed. This strongly contrasts with the canonical quantum critical point behavior observed in chemically modified systems such as Ni(S,Se)2 and V2O3. We propose that the presence of two distinct Fermi surface segments is responsible for the observed unusual behaviors.