Quantum Phase Diagram and Spontaneously Emergent Topological Chiral Superconductivity in Doped Triangular-Lattice Mott Insulators

TL;DR

This paper demonstrates the realization of a topological chiral superconducting state with spontaneous time-reversal symmetry breaking in doped triangular-lattice Mott insulators, revealing a rich phase diagram driven by geometrical frustration and hole dynamics.

Contribution

It provides the first large-scale DMRG study showing a $d+id$-wave chiral topological superconductor in a doped triangular-lattice $t$-$J$ model, mapping out its phase diagram.

Findings

Identification of a $d+id$-wave chiral TSC with Chern number $C=2$

Discovery of a pseudogap-like phase with charge stripe order

Observation of a transition from TSC to $d$-wave superconductivity with increased NNN coupling

Abstract

The topological superconducting state is a highly sought-after quantum state hosting topological order and Majorana excitations. In this work, we explore the mechanism to realize the topological superconductivity (TSC) in the doped Mott insulators with time-reversal symmetry (TRS). Through large-scale density matrix renormalization group study of an extended triangular-lattice $t$-$J$ model on the six- and eight-leg cylinders, we identify a $d+id$-wave chiral TSC with spontaneous TRS breaking, which is characterized by a Chern number $C=2$ and quasi-long-range superconducting order. We map out the quantum phase diagram by tuning the next-nearest-neighbor (NNN) electron hopping and spin interaction. In the weaker NNN-coupling regime, we identify a pseudogaplike phase with a charge stripe order coexisting with fluctuating superconductivity, which can be tuned into $d$-wave superconductivity by increasing the doping level and system width. The TSC emerges in the intermediate-coupling regime, which has a transition to a $d$-wave superconducting phase with larger NNN couplings. The emergence of the TSC is driven by geometrical frustrations and hole dynamics which suppress spin correlation and charge order, leading to a topological quantum phase transition.