Gapless spin liquid state of the spin-1/2 honeycomb antiferromagnetic Gamma model*

We propose a choreographed model by introducing a bond-modulated Heisenberg interaction J in addition to the Gamma term. With varying an angular parameter of vartheta= atan}(Gamma/J)in[0,pi], the ground state is shown to change from a zigzag magnetic order to a stripy magnetic order through a mixed phase as well as a noncoplanar phase based on a parallel tempering Monte Carlo simulation. In the quantum case where we resort to large scale density matrix renormalization group calculations, two classical intermediate phases merge into one which is gapless and nonmagnetic, signaling a quantum spin liquid (QSL), in a wide range of 0.50\leq vartheta/pi\leq 0.66(1) for the thermodynamic limit. It turns out that the ground state of HCGammaA is affirmed to be the gapless QSL since it corresponds to vartheta=\pi/2 in the phase diagram. Our findings are further verified with scanning the variable parameter vartheta on a long cylinder.