Browsing by Author "Taniguchi, Takashi"

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    Open Access
    Exciton diffusion in two-dimensional chiral perovskites
    (Technische Universität Dresden, 2024-11-07) Terres, Sophia; Scalon, Lucas; Brunner, Julius; Horneber, Dominik; Düreth, Johannes; Huang, Shiyu; Taniguchi, Takashi; Watanabe, Kenji; Nogueira, Ana Flávia; Höfling, Sven; Klembt, Sebastian; Vaynzof, Yana; Chernikov, Alexey
    This contains the data underpinning our recent paper on chiral 2D perovskites, uploaded on ArXiv (https://doi.org/10.48550/arXiv.2408.05946) in 2024. The abstract of the article is reproduced below: Two-dimensional (2D) organic-inorganic hybrid perovskites emerged as a versatile platform for light-emitting and photovoltaic applications due to their unique structural design and chemical flexibility. Their properties depend heavily on both the choice of the inorganic lead halide framework and the surrounding organic layers. Recently, the introduction of chiral cations into 2D perovskites has attracted major interest due to their potential for introducing chirality and tuning the chiro-optical response. Importantly, the optical properties in these materials are dominated by tightly bound excitons that also serve as primary carriers for the energy transport. The mobility of photoinjected excitons is thus important from the perspectives of fundamental material properties and optoelectronic applications, yet remains an open question. Here, we demonstrate exciton propagation in a 2D chiral perovskite methylbenzylammonium lead iodide (MBA2PbI4) using transient photoluminescence microscopy and reveal density-dependent transport over more than 100 nanometers at room temperature with diffusion coefficients as high as 2 cm2/s. We observe two distinct regimes of initially rapid diffusive propagation and subsequent localization. Moreover, perovskites with enantiomer pure cations are found to exhibit faster exciton diffusion compared to the race-mic mixture, correlated with the impact of the material composition on disorder. Altogether, the observations of efficient exciton diffusion at room temperature highlight the potential of 2D chiral perovskites to merge chiro-optical properties with strong light-matter interaction and efficient energy transport.
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    Open Access
    Ultrafast switching of trions in 2D materials by terahertz photons
    (Technische Universität Dresden, 2024-11-14) Venanzi, Tommaso; Cuccu, Marzia; Perea Causin, Raul; Sun, Xiaoxiao; Brem, Samuel; Erkensten, Daniel; Taniguchi, Takashi; Watanabe, Kenji; Malic, Ermin; Helm, Manfred; Winnerl, Stephan; Chernikov, Alexey
    External control of optical excitations is key for manipulating light–matter coupling and is highly desirable for photonic technologies. Excitons in monolayer semiconductors emerged as a unique nanoscale platform in this context, offering strong light–matter coupling, spin–valley locking and exceptional tunability. Crucially, they allow electrical switching of their optical response due to efficient interactions of excitonic emitters with free charge carriers, forming new quasiparticles known as trions and Fermi polarons. However, there are major limitations to how fast the light emission of these states can be tuned, restricting the majority of applications to an essentially static regime. Here we demonstrate 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 is based on a rapid conversion of trions to excitons by absorption of terahertz photons inducing photodetachment. Monitoring time-resolved emission dynamics in optical-pump/terahertz-push experiments, we achieve the required resonance conditions as well as demonstrate tunability of the process with delay time and terahertz pulse power. Our results introduce a versatile experimental tool for fundamental research of light-emitting excitations of composite Bose–Fermi mixtures and open up pathways towards technological developments of new types of nanophotonic device based on atomically thin materials.