4 A lower symmetry dispersion relation

From here you may load this preset , see the text of the next , or return to the preset list.

Here is a crystal in which the effective mass, even at the origin of k-space, is anisotropic. (Although the lattice is still nominally square, the electronic structure is such that the x- and y-directions are no longer equivalent.)

The applied electric field is at 45 degrees to the x-axis. Compare the orientations of the trajectories in real and in k-space and explain.