Spin states of holes in Ge/Si nanowire quantum dots.
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.
Roddaro
S
S
Solid State Physics/The Nanometer Structure Consortium, Lund University, P.O. Box 118, S-221 00 Lund, Sweden.
Fuhrer
A
A
Brusheim
P
P
Fasth
C
C
Xu
H Q
HQ
Samuelson
L
L
Xiang
J
J
Lieber
C M
CM