title: Spin states of holes in Ge/Si nanowire quantum dots.
abstract: We investigate tunable hole quantum dots defined by surface gating Ge/Si core-shell nanowire heterostructures. In single level Coulomb-blockade transport measurements at low temperatures spin doublets are found, which become sequentially filled by holes. Magnetotransport measurements allow us to extract a g factor g approximately 2 close to the value of a free spin-1/2 particle in the case of the smallest dot. In less confined quantum dots smaller g factor values are observed. This indicates a lifting of the expected strong spin-orbit interaction effects in the valence band for holes confined in small enough quantum dots. By comparing the excitation spectrum with the addition spectrum we tentatively identify a hole exchange interaction strength chi approximately 130 microeV.
authors.affiliation: Solid State Physics/The Nanometer Structure Consortium, Lund University, P.O. Box 118, S-221 00 Lund, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Roddaro
authors.forename: A
authors.initials: A
authors.lastname: Fuhrer
authors.forename: P
authors.initials: P
authors.lastname: Brusheim
authors.forename: C
authors.initials: C
authors.lastname: Fasth
authors.forename: H Q
authors.initials: HQ
authors.lastname: Xu
authors.forename: L
authors.initials: L
authors.lastname: Samuelson
authors.forename: J
authors.initials: J
authors.lastname: Xiang
authors.forename: C M
authors.initials: CM
authors.lastname: Lieber