Spontaneous spin-splitting observed in resonant tunneling diode with narrow band-gap asymmetric quantum well

This paper deals with the experiments to observe the spontaneous spin-splitting (SSS) in the resonant tunneling diode (RTD), which was specially designed to have a narrow band gap as well as an asymmetric potential well. In current-voltage (I-V) characteristics, there observed a current peak doubly splitted (denoted as P_1-1 and P_1-2) at low bias field. The difference of the derivative peak height of P_1-1 between those with and without the parallel magnetic field (dI/dV(B)-dI/dV(B = 0)), which was applied along the easy axis of the emitter electrode, increased with increasing field strength, while the quantity of P_1-2 stayed almost zero. The increase of the difference of the derivative peak height of P_1-1 was found to saturate almost at the coercive field of the electrode. It was also found that those variations of the derivative peak height were observed only in the case of electron injection via the ferromagnetic (NiFe) emitter electrode. The amount of splitting (∼15 meV) observed was almost the same as those estimated from magnetoresistance measurements. These results suggest that the observed splitted peak is intimately related to the SSS expected at the center well in our unique RTDs.