Thursday, November 15, 2012

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.

No comments:

Post a Comment