Towards the understanding of fully-heavy tetraquark states from various models.

We use a color-magnetic interaction model, a traditional constituent quark model and a multiquark color flux-tube model to systematically investigate the properties of the fully-heavy tetraquark states $[Q_1Q_2][\bar{Q}_3\bar{Q}_4]$ ($Q=c,b$) with the help of the Gaussian expansion method. Numerical results indicate that the color-magnetic interaction model can not completely absorb QCD dynamic effects through effective constituent quark mass in the states $[Q_1Q_2][\bar{Q}_3\bar{Q}_4]$. In addition, the model may overestimate the color-magnetic interaction in the extension from heavy mesons to the states $[Q_1Q_2][\bar{Q}_3\bar{Q}_4]$ under the assumption of same spatial configurations. The Coulomb interaction plays a critical role in the dynamical model calculations on the heavy hadrons, which is the direct reason why none of bound states $[Q_1Q_2][\bar{Q}_3\bar{Q}_4]$ can be found in the dynamical models. The color configuration $\left[[Q_1Q_2]_{\mathbf{6}_c}[\bar{Q}_3\bar{Q}_4]_{\bar{\mathbf{6}}_c}\right]_{\mathbf{1}}$ should be taken seriously in the ground states due to the strong Coulomb attraction. The color configuration $\left[[Q_1Q_2]_{\bar{\mathbf{3}}_c}[\bar{Q}_2\bar{Q}_4]_{\mathbf{3}_c}\right]_{\mathbf{1}}$ is absolutely dominant in the excited states mainly because of the lower kinetic induced by the Coulomb interaction.