Doped t-J Model on a Triangular Lattice: Possible Application to Na$_x$CoO$_2\cdot y$H$_2$0 and Na$_{1-x}$TiO$_2$

TL;DR

This paper predicts a time-reversal-symmetry-breaking superconducting state in a doped t-J model on a triangular lattice, which could explain phenomena in certain doped Mott insulators like Na$_x$CoO$_2$·yH$_2$O.

Contribution

It introduces a novel superconducting ground state with broken time-reversal symmetry in the t-J model on a triangular lattice, relevant to specific doped Mott insulators.

Findings

Superconducting state with $d_{x^2-y^2}+ id_{xy}$ symmetry found in the model.

Superconductivity occurs at low doping levels for specific t/J ratios.

Potential relevance to experimental observations in Na$_x$CoO$_2$·yH$_2$O.

Abstract

We report the finding of time-reversal-symmetry-breaking $d_{x^2-y^2}+ id_{xy}$ superconducting ground state in the slave-boson mean-field theory for the t-J model on triangular lattice. For $t/J=-5$ ($t/J=-9$) pairing exists for $x < 13%$ ($x<8%$) upon electron doping, and $x <56%$ ($x<13%$) upon hole doping. These results are potentially relevant to doped Mott insulators Na$_x$CoO$_2$.yH$_2$O and Na$_{1-x}$TiO$_2$.