Detection Kondo effect in graphene quantum dots

摘要

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 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 Kondo effect. We evaluated Kondo temperature ~ 4 K from the width of zero-bias conductance.