Mott Transition in Degenerate Hubbard Models: Application to Doped Fullerenes

TL;DR

This paper investigates the Mott-Hubbard transition in degenerate Hubbard models, proposing a relation between interaction strength and degeneracy, supported by computational methods, and applies findings to doped fullerenes suggesting they are near this transition.

Contribution

It introduces a conjecture that the Mott-Hubbard transition occurs at U/W proportional to the square root of degeneracy N, supported by numerical calculations and applied to real materials.

Findings

Transition occurs at U/W ∝ √N, supported by simulations.

Doped fullerenes like A3C60 are near the Mott transition.

Realistic parameters indicate a correlated metallic state.

Abstract

The Mott-Hubbard transition is studied for a Hubbard model with orbital degeneracy N, using a diffusion Monte-Carlo method. Based on general arguments, we conjecture that the Mott-Hubbard transition takes place for U/W \propto \sqrt{N}, where U is the Coulomb interaction and W is the band width. This is supported by exact diagonalization and Monte-Carlo calculations. Realistic parameters for the doped fullerenes lead to the conclusion that stoichiometric A_3 C_60 (A=K, Rb) are near the Mott-Hubbard transition, in a correlated metallic state.