  Using tensor network states to unravel the physics of quantum spin liquids in
minimal, yet generic microscopic spin or electronic models remains notoriously
challenging. A prominent open question concerns the nature of the insulating
ground state of two-dimensional half-filled Hubbard-type models on the
triangular lattice in the vicinity of the Mott metal-insulator transition, a
regime which can be approximated microscopically by a spin-1/2 Heisenberg model
supplemented with additional "ring-exchange" interactions. Using a novel and
efficient state preparation technique whereby we initialize full density matrix
renormalization group (DMRG) calculations with highly entangled
Gutzwiller-projected Fermi surface trial wave functions, we show -- contrary to
previous works -- that the simplest triangular lattice $J$-$K$ spin model with
four-site ring exchange likely does not harbor a fully gapless U(1) spinon
Fermi surface (spin Bose metal) phase on four- and six-leg wide ladders. Our
methodology paves the way to fully resolve with DMRG other controversial
problems in the fields of frustrated quantum magnetism and strongly correlated
electrons.
