Use the Lorentz Force node to add the contribution from the magnetic vector potential A to the kinetic momentum P, given by

Note that there is no minus sign in front of the imaginary unit i because of the engineering sign convention adopted by all COMSOL physics interfaces: a plane wave is exp(−ikx  +  iωt), not exp(ikx  −  iωt).

The Lorentz Force node adds the second term in Equation 5-2. Enter the magnetic vector potential components in units of Wb/m. The default is 0.