The semiclassical motion of the particle can be described by a closed loop in k-space. Throughout this loop, the particle maintains a constant energy, as well as a constant momentum along the magnetic field axis. By defining A to be the k -space area enclosed by this loop (this area depends on the energy E, the direction of the magnetic field, and the on-axis wavevector k B), then it can be shown that the cyclotron effective mass depends on the band structure via the derivative of this area in energy: