The interaction between the particles of the many-body system does not need to be small (see e.g. electrons in a metal).

In practice, a lattice as many-body systems includes interactions between electrons and nuclei in potential, but this calculation can be too intricate.

The interaction between the particles of the many-body system does not need to be small.

Coupled cluster (CC) is a numerical technique used for describing many-body systems.

In many-body systems, several of the relevant states have an energy difference that matches with the energy of a THz photon.

At the same time, they constitute an interesting many-body system whose quantum properties can be modified, e.g., via a nanostructure design.

Calculations in many-body systems are difficult and require advanced computation techniques.

A many-body system with interactions is generally very difficult to solve exactly, except for extremely simple cases (random field theory, 1D Ising model).

The transition describes an abrupt change in the ground state of a many-body system due to its quantum fluctuations.

There is nowadays a considerable interest in the field of quantum theory for computational methods well-suited to the physics of many-body systems.