Understanding and controlling charge dynamics in single optical emitters, including charge fluctuations and charge transfer, are of increasing importance for the design of well-behaved quantum optoelectronic systems. Charge fluctuations can induce spectral diffusion, a ubiquitous process randomizing the spectral mode of single optical emitters at cryogenic temperatures via a dynamic quantum-confined Stark effect. Charge transfer is a critical step in forming charged excited states with altered emission properties and differing spin-physics. In this talk, I highlight our recent progress towards understanding and controlling charge-transfer and charge-fluctuations by optical means. First, I present a study of spectral diffusion in nascent quantum emitters using photon-correlation Fourier spectroscopy (PCFS). PCFS can measure the bandwidth and kinetics of spectral fluctuations down to nanosecond timescales. Using PCFS, we show how quantum emitters in 2D hexagonal boron nitride exhibit multi-timescale discrete spectral jumping that can be attributed to at least two characteristic charge fluctuation time constants. [1,2] Second, I demonstrate how ultrafast mid-infrared pulses can drive charge-transfer in single colloidal semiconductor quantum dot heterostructures. I introduce a compound experiment of ultrafast and single-molecule spectroscopy that measures the rate constants of field-induced carrier tunneling across the quantum dot heterostructure. [3] Broadly, my presentation suggests the general utility of our techniques to study charge dynamics in the limit of various single emitters.

Studying charge-transfer and charge-noise in single emitters with ultrafast and photon-correlation spectroscopy

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