Optical initialization of a single spin-valley in charged WSe₂ quantum dots

Area of Science:

• Condensed Matter Physics
• Quantum Information Science
• Materials Science

Background:

• Single charge and spin control are key for quantum information technology, spintronics, and quantum sensing.
• Atomically thin transition-metal dichalcogenide monolayers are promising for valleytronics due to their spin-valley locked index.
• Previous research focused on ensemble control, with single charge valley control remaining unexplored due to short exciton lifetimes.

Purpose of the Study:

• To provide evidence for localized single holes with net spin in WSe2 quantum dots.
• To demonstrate the initialization of the spin-valley state of individual charges using laser helicity.
• To explore the potential for single-charge-based valleytronics and its implications for quantum technologies.

Main Methods:

• Utilized optically active WSe2 quantum dots.
• Employed laser excitation with specific helicity under small magnetic fields to initialize spin-valley states.
• Measured recombination times to estimate valley lifetimes of single charges.

Main Results:

• Unambiguous evidence for localized holes with net spin in WSe2 quantum dots was observed.
• Successful initialization of the spin-valley state of single charges was achieved using polarized light.
• A lower bound for the single-charge valley lifetime in quantum dots was estimated to be in the nanosecond range.

Conclusions:

• The study extends two-dimensional valleytronics to the single spin-valley level.
• The presence of excess charge in quantum dots significantly prolongs valley lifetime, unlike in neutral quantum dots.
• Findings have significant implications for developing quantum information processing and quantum sensing technologies.