Correlation between elliptic flow and shear viscosity in intermediate-energy heavy-ion collisions

The correlation between the elliptic flow $v_2$ scaled by the impact parameter $b$ and the shear viscosity $\eta$ as well as the specific viscosity $\eta/s$, defined as the ratio of the shear viscosity to the entropy density $s$, is investigated for the first time in intermediate-energy heavy-ion collisions based on an isospin-dependent quantum molecular dynamic model. The elliptic flow is calculated at balance energies to exclude the geometric influence such as the blocking effect from the spectators. Our study shows that $v_{2}/b$ decreases almost linearly with increasing $\eta$, consistent with that observed in ultra-relativistic heavy-ion collisions. On the other hand, $v_{2}/b$ is found to increase with increasing $\eta/s$.