Monte Carlo study of an unconventional superconducting phase in Ir-oxide J_{eff}=1/2 Mott insulators induced by carrier doping

TL;DR

This study uses variational Monte Carlo simulations to demonstrate that electron doping induces an unconventional d-wave superconducting phase in Ir-based Mott insulators with strong spin-orbit coupling, revealing potential parallels with high-T_c cuprates.

Contribution

The paper presents the first microscopic theoretical evidence of superconductivity induced by carrier doping in J_{eff}=1/2 Mott insulators, highlighting the role of multi-orbital effects and spin-orbit coupling.

Findings

Superconductivity appears only with electron doping, not hole doping.

The superconducting state has a d_{x^2-y^2}-wave pseudospin singlet symmetry.

The results suggest similarities between Ir-oxide superconductors and high-T_c cuprates.

Abstract

Based on a microscopic theoretical study, we show that novel superconductivity is induced by carrier doping in layered perovskite Ir oxides where a strong spin-orbit coupling causes an effective total angular momentum J_{eff}=1/2 Mott insulator. Using a variational Monte Carlo method, we find an unconventional superconducting state in the ground state phase diagram of a t_{2g} three-orbital Hubbard model on the square lattice. This superconducting state is characterized by a d_{x^2-y^2}-wave "pseudospin singlet" formed by the J_{eff}=1/2 Kramers doublet, which thus contains inter-orbital as well as both singlet and triplet components of t_{2g} electrons. The superconducting state is found stable only by electron doping, but not by hole doping, for the case of carrier doped Sr_2IrO_4. We also study an effective single-orbital Hubbard model to discuss the similarities to high-T_c cuprate superconductors and the multi-orbital effects.