The Kondo effect observed up to TK∼80 K in self-assembled InAs quantum dots laterally coupled to nanogap electrodes

We have fabricated single electron tunneling structures by forming nanogap metallic electrodes directly upon single self-assembled InAs quantum dots (QDs). The fabricated samples exhibited clear Coulomb blockade effects. Furthermore, Kondo effect was observed when strong coupling between the electrodes and the QD was realized using a large QD with a diameter of ∼100 nm. From the temperature dependence of the linear conductance at the Kondo valley, the Kondo temperature TK was determined to be ∼81 K. This is the highest TK ever reported for artificial quantum nanostructures. The observed very high TK is due to strong QD–electrode coupling and large charging/orbital-quantization energies in the present self-assembled InAs QD structures.