$\textit{Ab initio}$ Method for Examining the Halo Structure of $^6$He*

We solve for the ground states of $^4$He and $^6$He with $\textit{ab initio}$ configuration interaction methods using the Daejeon16 nucleon-nucleon (NN) interaction. Using the full ground state wave functions, we evaluate pairwise correlations to characterize the structures of these two systems. First, we examine the pairwise correlations in the individual NN channels to isolate the similarities and differences of these two systems. We then evaluate and compare the coordinate-space separations of the two-proton subsystem, the neutron-proton pairs and the neutron-neutron pairs for these two systems. Finally, we use these coordinate-space pair correlations to address the halo structure of $^6$He relative to $^4$He.