  The search for exotic quantum spin liquid states in simple yet realistic spin
models remains a central challenge in the field of frustrated quantum
magnetism. Here we consider the canonical nearest-neighbor kagome Heisenberg
antiferromagnet restricted to a quasi-1D strip consisting entirely of
corner-sharing triangles. Using large-scale density matrix renormalization
group calculations, we identify in this model an extended gapless quantum phase
characterized by central charge $c=2$ and power-law decaying spin and
bond-energy correlations which oscillate at tunably incommensurate wave
vectors. We argue that this intriguing spin liquid phase can be understood as a
marginal instability of a two-band spinon Fermi surface coupled to an emergent
U(1) gauge field, an interpretation which we substantiate via bosonization
analysis and Monte Carlo calculations on model Gutzwiller variational wave
functions. Our results represent one of the first numerical demonstrations of
emergent fermionic spinons in a simple SU(2) invariant nearest-neighbor
Heisenberg model beyond the strictly 1D (Bethe chain) limit.
