Nanoscale confinement and control of excitonic complexes in a monolayer WSe2
arxiv(2023)
Abstract
Nanoscale control and observation of photophysical processes in
semiconductors is critical for basic understanding and applications from
optoelectronics to quantum information processing. In particular, there are
open questions and opportunities in controlling excitonic complexes in
two-dimensional materials such as excitons, trions or biexcitons. However,
neither conventional diffraction-limited optical spectroscopy nor
lithography-limited electric control provides a proper tool to investigate
these quasiparticles at the nanometer-scale at cryogenic temperature. Here, we
introduce a cryogenic capacitive confocal optical microscope (C3OM) as a tool
to study quasiparticle dynamics at the nanometer scale. Using a conductive
atomic force microscope (AFM) tip as a gate electrode, we can modulate the
electronic doping at the nanometer scale in WSe2 at 4K. This tool allows us to
modulate with nanometer-scale confinement the exciton and trion peaks, as well
a distinct photoluminescence line associated with a larger excitonic complex
that exhibits distinctive nonlinear optical response. Our results demonstrate
nanoscale confinement and spectroscopy of exciton complexes at arbitrary
positions, which should prove an important tool for quantitative understanding
of complex optoelectronic properties in semiconductors as well as for
applications ranging from quantum spin liquids to superresolution measurements
to control of quantum emitters.
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