Chaotic behavior in the magneto-resistance of quantum dot and quantum point contact

We have investigated quantum structures, such as narrow wires, single or coupled quantum dots (QDs), and quantum point contact (QPC), in order to clarify the origin of the chaotic and fractal behavior in their transport properties. Chaotic behavior in the electrical transport in QD and QPC has been studied in the low temperature magneto-resistance (MR), and by use of scanning gate microscopy (SGM). The quantum structures are fabricated using hetero-junction semiconductors. The low temperature MR has been measured using a 3He cryostat or dilution refrigerator with magnetic fields up to 8 T. We discuss the relation between the narrow constrictions in these structures and chaotic scatterings observed in the MR and SGM. (author)