Low energy electronic states and triplet pairing in layered cobaltates

TL;DR

This paper investigates the low-energy electronic states in layered cobaltates, emphasizing the role of spin-orbit coupling and proposing a novel t-J model that supports unconventional triplet pairing.

Contribution

It introduces a new effective t-J model based on mixed spin-orbital states, differing from cuprates, to explain triplet pairing in layered cobaltates.

Findings

Spin-orbit coupling significantly affects the Fermi surface at low doping.

The proposed t-J model supports pseudospin-triplet pairing.

Electronic states originate from the Mott insulating limit.

Abstract

The structure of the low-energy electronic states in layered cobaltates is considered starting from the Mott insulating limit. We argue that the coherent part of the wave-functions and the Fermi-surface topology at low doping are strongly influenced by spin-orbit coupling of the correlated electrons on the $t_{2g}$ level. An effective t-J model based on mixed spin-orbital states is radically different from that for the cuprates, and supports unconventional, pseudospin-triplet pairing.