A Zero-Bias Conductance Anomaly due to Kondo Effect in Graphene Quantum Dots
Graphene is suitable material for keeping electron spin states and expected for spintronics devices because of weak spin-orbit interaction and weak nuclear spin interaction. From this reason, spin-correlation phenomena are investigated in graphene. Kondo effect in quantum dot is forming spin singlet state between electrons in leads and a dot and one of the spin correlation effects in quantum dots. Here, we will report Kondo effect in a graphene quantum dot. We fabricated graphene quantum dots by electron-beam lithography and reactive-ion etching from chemical-vapor-deposition graphene. We measured graphene quantum dots at T ~ 20 mK by a dilution refrigerator. We observed zero-bias anomaly at Coulomb blockade in graphene quantum dots. As magnetic field increases, the zero-bias conductance was suppressed. These results indicate that the zero bias anomaly comes from Kondo effect. We evaluated Kondo temperature ~ 4.8 K from the width of zero-bias conductance.
Keywords: Graphene, Quantum dot, Kondo effect, Transport.