Thermodynamics of a bad metal-Mott insulator transition in the presence of frustration
We study the temperature dependence of a range of thermodynamic properties (charge susceptibility, specific heat, entropy and spin susceptibility) of the Hubbard model on the anisotropic triangular lattice at half filling by means of the numerical finite-temperature Lanczos method. This Hubbard model describes several important families of superconducting organic charge transfer salts.
The results include
- Clear signatures of a metal-Mott insulator transition in the charge susceptibility.
- The metal-insulator transition can be driven either by increasing interactions or by reducing frustration.
- The metallic phase is characterized by a small charge susceptibility, large entropy, low coherence temperature, large renormalized quasiparticle mass, and large spin susceptibility.
- The coherence temperature corresponds to destruction of quasi-particles and crossover from a Fermi liquid to a bad metal. Our estimate of the temperature is comparable to what is observed in the organics.
- The local magnetic moment in the metallic phase is large and comparable to the local moment in the insulating phase. This is characteristic of a bad metal.
- Frustration increases the density of low-lying spin excitations in the Mott insulating phase and decreases longer range spin correlations.