  Polarons are quasiparticles formed as a result of lattice distortions induced
by charge carriers. The single-electron Holstein model captures the
fundamentals of single polaron physics. We examine the power of the exponential
ansatz for the polaron ground-state wavefunction in its coupled cluster,
canonical transformation, and (canonically transformed) perturbative variants
across the parameter space of the Holstein model. Our benchmark serves to guide
future developments of polaron wavefunctions beyond the single-electron
Holstein model.
