  The comprehensive understanding of superconductivity is a multi-scale task
that involves several levels, starting from the electronic scale determining
the microscopic mechanism, going to the phenomenological scale describing
vortices and the continuum-elastic scale describing vortex matter, to the
macroscopic scale relevant in technological applications. The prime example for
such a macro-phenomenological description is the Bean model that is hugely
successful in describing the magnetic and transport properties of bulk
superconducting devices. Motivated by the development of novel devices based on
superconductivity in atomically thin films, such as twisted-layer graphene,
here, we present a simple macro-phenomenological description of the critical
state in such two-dimensional (2D) thin films. While transverse screening and
demagnetization can be neglected in these systems, thereby simplifying the task
in comparison with usual film- and platelet shaped samples, surface and bulk
pinning are important elements to be included. We use our 2D critical state
model to describe the transport and magnetic properties of 2D thin-film
devices, including the phenomenon of non-reciprocal transport in devices with
asymmetric boundaries and the superconducting diode effect.
