Transverse electron momentum distributions in strong-field ionization: nondipole and Coulomb focusing effects

In strong-field ionization, the combined influence of nondipole and Coulomb focusing effects leave a unique signature on the photoelectron momentum distributions, which may have direct implications on many important strong-field phenomena. We present a comprehensive review of the experimental and theoretical investigations on these effects. We classify these investigations by relativistic and non-relativistic modelling based on different theoretical approaches, e.g. classical, semiclassical, strong-field approximation, time-dependent Schrodinger equation, and time-dependent Dirac equation. Finally, we discuss the latest experimental and theoretical development on this subject that has undergone so far in order to deeply understand the underlying physics.