Spin-dependent energy relaxation inside a quantum dot

We employ pulse excitation measurements in order to investigate spin-dependent energy relaxation inside a quantum dot. A fast pulse signal is applied to a gate electrode in order to excite a quantum dot, and the induced transient current is analyzed in terms of energy relaxation. We describe transient current measurements on a lateral quantum dot, in which the tunneling rates are controllable with gate voltages, and on a vertical quantum dot, in which the total number of electrons and total spin can be well identified. The spin-conservation rule during energy relaxation is clearly identified.