Abstract:

Hole semiconductor spintronics is very interesting due most diluted magnetic semiconductors being p-type. More importantly from a physics point of view, the spin-3/2 character of states in the topmost valence band of semiconductors can lead to intricate and sometimes counterintuitive quantum phenomena in hole nanostructures. Two examples are the strong anisotropies of the effective g-factors of two-dimensional hole gases [1], and hole quantum point contacts [2]. Confinement effects appear to drastically influence the spin polarization of hole systems and provide an avenue for hole spin manipulation.
In this work, we theoretically investigate the effects of confinement on spin splitting in cylindrical hole nanowires. An anomalous spin polarization is found to result from a complex interplay between heavy-hole-light-hole splitting, confinement, and symmetry. In particular, we find that the effective g-factors are fluctuating strongly between different wire levels. These findings are universal, i.e., radius-independent, for a given material. Strikingly, some levels have a vanishing g-factor, indicating total lack of polarization. Using an invariant expansion of the spin-3/2 hole density matrix [3], we have investigated in detail the origin of the fluctuations and the complete g-factor suppressions of some of the levels. We found intriguing radially dependent spin textures which directly correlate with the magnitude of the g-factors. Furthermore, we find very interesting dependence of the g-factors on the spin-orbit coupling strength in the valence band. This may open up avenues for hole g-factor manipulation, e.g., in heterostructured nanowires.
 
 
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