Mass enhancement and magnetic order at the Mott-Hubbard transition

We study the evolution with pressure P and band filling y of the heat capacity, Hall coefficient, and resistivity at the approach to the T→0 Mott-Hubbard metal-insulator transition (MIT) in highly correlated ${\mathrm{V}}_{2\mathrm{-}\mathit{y}}$ ${\mathrm{O}}_3$. Under P, the electronic effective mass ${\mathit{m}}^{\mathrm{*}}$ diverges at the MIT with a negligible change in carrier concentration n away from half-filling. Conversely, in the doped system ${\mathit{m}}^{\mathrm{*}}$ actually decreases as the MIT is approached, while n increases linearly with y. The low-T magnetic order in the metal helps us deconvolute contributions from charge correlations and spin fluctuations.