In a recent paper, the authors stress the difference between single-body tunneling and many-body tunneling (at the atomic level): "In contrast to the well-studied incoherent single-particle tunnelling, our understanding of many-body tunnelling is still in its infancy." https://www.nature.com/articles/nphys3225
When considering tunneling at the nuclear level such as in the case of alpha emission or nuclear fusion, the approach typically employed involves solving the wave equation for a particle that tunnels through a potential barrier. To do that, techniques like the WKB approximation are used (see https://en.wikipedia.org/wiki/Quantum_tunnelling#The_WKB_approximation). However, it seems that the underlying assumption here is that the tunneling process is single-particle tunneling.
In contrast, has there been any treatment of many-body tunneling at the nuclear level?