Pseudogap in organic charge transfer salts

This post follows up on earlier posts including
Connecting the pseudogap to superconductivity in the organics

There is a nice paper
Pseudogap and Fermi arc in κ-type organic superconductors
by Jing Kang, Shun-Li Yu, Tao Xiang, and Jian-Xin Li

They use Cluster Perturbation Theory to study the Hubbard model on the anisotropic triangular lattice at half filling. They calculate the one-electron spectral function using clusters as large as 12 sites [embedded self-consistently in an infinite lattice].

The authors find three distinct phases: Mott insulator, Fermi liquid, and a pseudogap state with Fermi arcs. The latter occurs in between the two other phases.

The Figure below shows an intensity map of the spectral function at the Fermi energy for U=4t and t'=0.7t. This clearly shows a complete Fermi surface (with hot spots).

As U increases towards the Mott phase, U=5t one sees parts of the Fermi surface gap out leaving Fermi arcs. Note the cold spots [red region=low scattering=large spectral density] occur at the same place as the nodes in the superconducting gap.

This is quite reminiscent of the physics that occurs in the cuprates and the doped Hubbard model.