Experimental realization of a ballistic spin interferometer based on the Rashba effect using a nanolithographically defined square loop array

We succeeded in observing gate-controlled electron spin interference in nanolithographically defined square loop arrays that were fabricated in In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As quantum wells (QWs). In this experiment, we demonstrated electron spin precession in ballistic channels within the QW that is caused by the Rashba effect. It turned out that the spin precession angle theta was gate controllable by more than 0.75 pi for a length of 1.5 mu m. Thus, the demonstration of the large controllability of theta by the applied gate voltage was carried out in a more direct way using spin interference of an electron wave function than the conventional beating analysis of the Shubnikov-de Haas oscillations.