Probing Electronic States in Monolayer Semiconductors through Static and Transient Third-Harmonic Spectroscopy

Abstract

Electronic states and their dynamics are of critical importance for electronic and optoelectronic applications. Here, we probe various relevant electronic states in monolayer MoS2, such as multiple excitonic Rydberg states and free-particle energy bands, with a high relative contrast of up to >200 via broadband (from ~1.79 to 3.10 eV) static third-harmonic spectroscopy, which is further supported by theoretical calculations. Moreover, we introduce transient third-harmonic spectroscopy to demonstrate that third-harmonic generation can be all-optically modulated with a modulation depth exceeding ~94% at ~2.18 eV, providing direct evidence of dominant carrier relaxation processes, associated with carrier-exciton and carrier-phonon interactions. Our results indicate that static and transient third-harmonic spectroscopies are not only promising techniques for the characterization of monolayer semiconductors and their heterostructures, but also a potential platform for disruptive photonic and optoelectronic applications, including all-optical modulation and imaging.

17 pages, 4 figures

References in corpus (7)

• Tightly bound excitons in monolayer WSe2
• Observation of Moiré Excitons in WSe2/WS2 Heterostructure Superlattices
• Probing Excitonic Dark States in Single-layer Tungsten Disulfide
• Non-linear Optical Spectroscopy of Excited Exciton States for Efficient Valley Coherence Generation in WSe2 Monolayers
• Engineering symmetry breaking in two-dimensional layered materials
• Third harmonic generation in graphene and few-layer graphite films
• All-optical polarization and amplitude modulation of second-harmonic generation in atomically thin semiconductors