We establish that a doping-driven first-order metal-to-metal transition, from a pseudogap metal to Fermi Liquid, can occur in correlated quantum materials. Our result is based on the exact Dynamical Mean Field Theory solution of the Dimer Hubbard Mod
el. This transition elucidates the origin of many exotic features in doped Mott materials, like the pseudogap in cuprates, incoherent bad metals, enhanced compressibility and orbital selective Mott transition. This phenomenon is suggestive to be at the roots of the many exotic phases appearing in the phase diagram of correlated materials.
The interaction-driven Mott transition in the half-filled Hubbard model is a first-order phase transition that terminates at a critical point $(T_mathrm{c},U_mathrm{c})$ in the temperature-interaction plane $T-U$. A number of crossovers occur along l
ines that extend for some range above $(T_mathrm{c},U_mathrm{c})$. Asymptotically close to $(T_mathrm{c},U_mathrm{c})$, these lines coalesce into the so-called Widom line. The existence of $(T_mathrm{c},U_mathrm{c})$ and of the associated crossovers becomes unclear when long-wavelength fluctuations or long-range order occur above $(T_mathrm{c},U_mathrm{c})$. We study this problem using continuous-time quantum Monte Carlo methods as impurity solvers for both Dynamical Mean-Field Theory (DMFT) and Cellular Dynamical Mean-Field Theory (CDMFT). We contrast the cases of the square lattice, where antiferromagnetic fluctuations dominate in the vicinity of the Mott transition, and the triangular lattice where they do not. The inflexion points and maxima found near the Widom line for the square lattice can serve as proxy for the triangular lattice case. But the only crossover observable in all cases at sufficiently high temperature is that associated with the opening of the Mott gap. The same physics also controls an analog crossover in the resistivity called the Quantum Widom line.
