Electrical control of hole spin relaxation in charge tunable InAs/GaAs quantum dots

Area of Science:

• Solid-state physics
• Quantum optics
• Semiconductor nanostructures

Background:

• Singly charged excitons, or trions, are crucial in semiconductor quantum dots.
• Optical orientation and spin dynamics in quantum dots are key for quantum information.
• Understanding charge and spin interactions is essential for device applications.

Purpose of the Study:

• To investigate the optical orientation of trions in charge-tunable InAs/GaAs quantum dots.
• To explore the effect of electric charge on trion photoluminescence polarization.
• To elucidate the mechanism controlling spin relaxation in quantum dots.

Main Methods:

• Optical orientation measurements on single self-assembled InAs/GaAs quantum dots.
• Charge-tunable device enabling variation of quantum dot charge from 0 to -2.
• Quasiresonant excitation and photoluminescence spectroscopy.
• Excitation spectroscopy and time-resolved measurements on quantum dot ensembles.

Main Results:

• Trion photoluminescence observed in charge-tunable quantum dots as charge varies from 0 to -2.
• Progressive polarization of trion photoluminescence from 0% to approximately 100% under quasiresonant excitation.
• Evidence of electric control over trion thermalization and hole-spin relaxation.
• Nanosecond timescale hole-spin relaxation driven by anisotropic electron-hole exchange.

Conclusions:

• Electric field provides precise control over trion spin polarization in quantum dots.
• Trion thermalization and hole-spin relaxation are key mechanisms influenced by electric charge.
• These findings offer pathways for electric-field-controlled spintronic and quantum devices.