Lande g factors and orbital momentum quenching in semiconductor quantum dots

TL;DR

This paper investigates how quantum confinement, strain, and geometry influence electron and hole g factors in semiconductor quantum dots, revealing orbital momentum quenching effects that alter expected magnetic properties.

Contribution

It demonstrates that quantum state quantization quenches orbital angular momentum, significantly modifying g factors beyond material and geometric effects.

Findings

Orbital momentum quenching pushes electron g factor towards 2.

g factors depend strongly on magnetic field orientation.

Quantum dot shape can be inferred from g factor asymmetry.

Abstract

We show that the electron and hole Lande g factors in self-assembled III-V quantum dots have a rich structure intermediate between that expected for paramagnetic atomic impurities and for bulk semiconductors. Strain, dot geometry, and confinement energy significantly modify the effective g factors of the semiconductor material from which the dot and barrier are constructed, yet these effects are insufficient to explain our results. We find that the quantization of the quantum dot electronic states further quenches the orbital angular momentum of the dot states, pushing the electron g factor towards 2, even when all the semiconductor constituents of the dot have negative g factors. This leads to trends in the dot's electron g factors that are the opposite of those expected from the effective g factors of the dot and barrier material. Both electron and hole g factors are strongly dependent on the magnetic field orientation; hole g factors for InAs/GaAs quatum dots have large positive values along the growth direction and small negative values in-plane. The approximate shape of a quantum dot can be determined from measurements of this g factor asymmetry.