Superconductivity in doped triangular Mott insulators: the roles of parent spin backgrounds and charge kinetic energy

TL;DR

This study uses density-matrix renormalization group calculations to explore how different spin backgrounds and hopping sign combinations influence superconductivity in doped triangular-lattice Mott insulators, highlighting the critical role of charge kinetic energy.

Contribution

It systematically investigates the effects of parent spin backgrounds and hopping signs on superconductivity, revealing that specific hopping parameters can induce superconductivity regardless of spin background.

Findings

Superconductivity can be achieved with finite next-nearest-neighbor hopping and specific sign combinations.

Superconducting phases are characterized by short-range spin correlations and stripe charge order.

Sign flips in hopping parameters can switch between superconducting, stripe, and pseudogap phases.

Abstract

We study the prerequisites for realizing superconductivity in doped triangular-lattice Mott insulators by considering three distinct parent spin backgrounds, i.e., $120^{\circ}$ antiferromagnets, quantum spin liquid, and stripy antiferromagnets, and all possible sign combinations $(\tau_1, \tau_2)$ of nearest-neighbor hopping and next-nearest-neighbor hopping $(t_1, t_2)$. Based on density-matrix renormalization group calculations, we find that, with finite $t_2$ and specific sign combinations $(\tau_1, \tau_2)$, the quasi-long-range superconductivity order can always be achieved, regardless of the nature of the parent spin backgrounds. Besides specific hopping signs $(\tau_1, \tau_2)$, these superconductivity phases in triangular lattices are commonly characterized by short-ranged spin correlations and two charges per stripe. In the robust superconductivity phase realized at larger $t_2/t_1$, flipping the signs $\tau_2$ and $\tau_1$ gives rise to the stripe phase without strong pairing and pseudogap-like phase without Cooper-pair phase coherence, respectively. Interestingly, the roles of the two hopping signs are switched at smaller $t_2/t_1$. Moreover, different sign combinations $(\tau_1, \tau_2)$ would stabilize distinct phases including superconductivity, charge density waves, spin density waves, and pseudogap-like phases accordingly. Our findings suggest the important role of charge kinetic energy in realizing superconductivity in doped triangular-lattice Mott insulators.