Roddaro S, Fuhrer A, Brusheim P, Fasth C, Xu H Q, Samuelson L, Xiang J, Lieber C M
Solid State Physics/The Nanometer Structure Consortium, Lund University, P.O. Box 118, S-221 00 Lund, Sweden.
Phys Rev Lett. 2008 Oct 31;101(18):186802. doi: 10.1103/PhysRevLett.101.186802. Epub 2008 Oct 27.
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.
我们研究了通过表面栅控锗/硅核壳纳米线异质结构定义的可调谐空穴量子点。在低温下单能级库仑阻塞输运测量中发现了自旋双重态，空穴会依次填充这些双重态。磁输运测量使我们能够提取一个g因子，在最小量子点的情况下，g约为2，接近自由自旋1/2粒子的值。在限制较小的量子点中观察到较小的g因子值。这表明对于限制在足够小量子点中的空穴，价带中预期的强自旋轨道相互作用效应有所减弱。通过将激发光谱与添加光谱进行比较，我们初步确定了空穴交换相互作用强度χ约为130微电子伏特。
