Spin-Related Current Suppression in a Semiconductor Quantum Dot Spin-Diode Structure

We experimentally study the transport features of electrons in a spin-diode structure consisting of a single semiconductor quantum dot (QD) weakly coupled to one nonmagnetic and one ferromagnetic (FM) lead, in which the QD has an artificial atomic nature. A Coulomb stability diamond shows asymmetric features with respect to the polarity of the bias voltage. For the regime of two-electron tunneling, we find anomalous suppression of the current for both forward and reverse bias. We discuss possible mechanisms of the anomalous current suppression in terms of spin blockade via the QD-FM interface at the ground state of a two-electron QD.

Figure 1

(a) Scanning electron micrograph of the lateral NM-QD-FM system. The dot size is $\sim 130\mathrm{nm}$. (b) Addition energy of electrons vs electron number for the QD used in this study.

Figure 2

(a) Differential conductance $dI/d{V}_{\mathrm{SD}}$ as a function of $V_{\mathrm{SD}}$ and $V_{\mathrm{G}}$ measured at 50 mK. The red and blue regions are the $dI/d{V}_{\mathrm{SD}}>0$ and $dI/d{V}_{\mathrm{SD}}<0$ regimes, respectively. The forward and reverse bias show the electron transport features from the FM to the QD and from the QD to the FM, respectively. (b) and (c) are representative $I\mathrm{\text{−}}{V}_{\mathrm{SD}}$ characteristics at $V_{\mathrm{G}}=0.75$, 0.85, 0.95, 1.05, and 1.30 V in the forward and reverse bias regimes, respectively.

Figure 3

Schematic diagrams of spin blockade under (a) forward and (b) reverse bias. For simplicity, the FM electrodes are illustrated as HMFs.

Figure 4

Enlarged $I\mathrm{\text{−}}{V}_{\mathrm{SD}}$ characteristics for various $V_{\mathrm{G}}$ in (a) forward and (b) reverse bias.