Entanglement in VQE ansatz in Qiskit

The Qiskit documentation on VQE describes two of the ansatz as "rotations with entanglements". The rotation gates are more or less clear, but the documentation doesn't mention what gate is used for entanglement. I suspect they use something like $$\exp(-i \alpha Z_1 Z_2)$$, but what exactly?

$$c\text{PHASE} = \begin{pmatrix} 1 & 0 & 0 & 0 \\ 0 & 1 & 0 & 0 \\ 0 & 0 & 1 & 0 \\ 0 & 0 & 0 & i \\ \end{pmatrix}$$
However, in hardware, one also uses the drift Hamiltonian $$U_{\text{ENT}}=\exp(-iH_0 \tau)$$, which naturally entangles all qubits.