Doped Mott Insulators in the Triangular Lattice Hubbard Model

TL;DR

This study explores how doping affects Mott insulators on a triangular lattice, revealing a novel chiral metallic state at intermediate coupling and various magnetic and superconducting phases as doping increases.

Contribution

It uncovers a new chiral metallic phase with long-range spin-chirality order and staggered loop currents at intermediate coupling, expanding understanding of doped Mott insulators.

Findings

Discovery of a chiral metal with spin-chirality order at intermediate coupling.

Persistence of 120-degree magnetic order at light doping in strong coupling.

Emergence of SDW order and hole pockets at moderate doping levels.

Abstract

We investigate the evolution of the Mott insulators in the triangular lattice Hubbard Model, as a function of hole doping $\delta$ in both the strong and intermediate coupling limits. Using the advanced density matrix renormalization group (DMRG) method, at light hole doping $\delta\lesssim 10\%$, we find a significant difference between strong and intermediate couplings. Notably, at intermediate coupling an unusual metallic state emerges, with short ranged spin correlations but long ranged spin-chirality order. Moreover, no clear Fermi surface or wave-vector is observed, this chiral metal also exhibits staggered loop current, which breaks the translational symmetry. These features disappear on increasing interaction strength or on further doping. At strong coupling, the 120 degree magnetic order of the insulating magnet persists for light doping, and produces hole pockets with a well defined Fermi surface. On further doping, $\delta \approx 10\%\sim 20\%$ SDW order and coherent hole Fermi pockets are found at both strong and intermediate couplings. At even higher doping $\delta \gtrsim 20\%$, the SDW order is suppressed and the spin-singlet Cooper pair correlations are simultaneously enhanced. We also briefly comment on the strong particle-hole asymmetry of the model.