The Electronic Structure of CdSe/CdS Core/Shell Seeded Nanorods: Type-I or Quasi-Type-II?

The electronic structure of CdSe/CdS core/shell seeded nanorods of experimentally relevant size is studied using a combination of molecular dynamics and semiempirical pseudopotential techniques, with the aim to address the transition from type-I to a quasi-type-II band alignment. The hole is found to be localized in the core region regardless of its size. The overlap of the electron density with the core region depends markedly on the size of the CdSe core: For small cores, we observe little overlap, consistent with type-II behavior. For large cores, significant core-overlap of a number of excitonic states can lead to type-I behavior. When electron-hole interactions are taken into account, the core-overlap is further increased. Our calculations indicate that the observed transition from type-II to type-I is largely due to simple volume effects, and not to band alignment.Comment: 6 pages, 4 figuer

Feasible Nanometric Magnetoresistance Devices

The electrical conductance through a ring is sensitive to the threading magnetic flux. It contains a component that is periodic with an Aharonov-Bohm (AB) period equal to the quantum flux. In molecular/atomic loops on the nanometer scale, encircling very small areas, the AB period involves unrealistically huge magnetic fields. We show that despite this, moderate magnetic fields can have a strong impact on the conductance. By controlling the lifetime of the conduction electron through a pre-selected single state that is well separated from other states due to the quantum confinement effect, we demonstrate that magnetic fields comparable to one Tesla can be used to switch a nanometric AB device. Using atomistic electronic structure calculations, we show that such effects can be expected for loops composed of monovalent metal atoms (quantum corals). Our findings suggest that future fabrication of nanometric magnetoresistance devices is feasible.Comment: 8 pages, 4 figure