Phys.org September 27, 2024
Excitons in monolayer semiconductors offer strong light–matter coupling, spin–valley locking and exceptional tunability allowing electrical switching of their optical response due to efficient interactions of excitonic emitters with free charge carriers forming trions and Fermi polarons. However, there are major limitations to how fast the light emission of these states can be tuned, restricting most applications to an essentially static regime. An international team of researchers (Italy, Sweden, Germany, Japan) demonstrated switching of excitonic light emitters in monolayer semiconductors on ultrafast picosecond time scales by applying short pulses in the terahertz spectral range following optical injection. The process was based on a rapid conversion of trions to excitons by absorption of terahertz photons inducing photo detachment. They achieved the required resonance conditions and demonstrated tunability of the process with delay time and terahertz pulse power. According to the researchers their work opens pathways towards technological developments of new types of nanophotonic device based on atomically thin materials… read more. TECHNICAL ARTICLE
Resonance conditions for the terahertz-induced trion-to-exciton conversion. Credit: Nature Photonics, 23 September 2024