Novel blockade due to spin-filtering with spin-orbit interaction

Abstract

We report experimental finding of current blockade in a quantum dot (QD), which effect originates from spin-filtering in a quantum point contact (QPC) with spin-orbit interaction (SOI). Our QPCs made of Ino.iGao.9 As showed clear Gq/2 plateaus (Gq ≡ 2e2/h), which suggest the spin-filtering. The effect has been further confirmed in the conduction of a QD defined by two such QPCs. The Kondo effect has been utilized for the clarification of the spin states in the QD and an ordinal Coulomb valley with spin 1/2 has been chosen for the stage to test the filtering. One of the bounding Coulomb peaks disappears with the applicaion of a finite source-drain voltage Vsd while the other grows in height. The sign reversal of Vsd transposes the heights of the two peaks. Further increase in |Vad| recovers the dual peak configuration. Every aspect of the above characteristics behavior is explained under the hypothesis of spin-filtering in the QPC at the plateau of Gq/2. From the peak height ratio, the lower bound of the filtering efficiency is estimated to be above 80%.