Pressure Induced Quantum Critical Point and Non-Fermi-Liquid Behavior in ${\mathrm{BaVS}}_3$

The phase diagram of ${\mathrm{BaVS}}_3$ is studied under pressure using resistivity measurements. The temperature of the metal to nonmagnetic Mott insulator transition decreases under pressure, and vanishes at the quantum critical point $p_{\mathrm{cr}}=20\mathrm{}\mathrm{kbar}$. We find two kinds of anomalous conducting states. The high-pressure metallic phase is a non-Fermi liquid described by $\Delta \rho \propto T^n$ where $n=1.2\mathrm{}–1.3$ at $1<T<\mathrm{}40\mathrm{}\mathrm{K}$. At $p<\mathrm{}{p}_{\mathrm{cr}}$, the transition is preceded by a wide precursor region with critically increasing resistivity which we ascribe to the opening of a soft Coulomb gap.