Shinichiro Matano | Searcharxiv

arXiv2026

Charge Filling-Dependent Valley Polarization and its Dynamics Driven by Correlated Interlayer Exciton States in WSe2/WS2 Heterobilayer

Moiré heterostructures of transition metal dichalcogenides provide an emerging platform for studying the strongly correlated electronic and excitonic states. The valley degree of freedom and its dynamics in the strongly correlated electronic and excitonic states in the moiré system are crucial for fundamental understanding and applications of valleytronics. Although the strongly correlated states in moiré systems have been extensively investigated, their impact on valley degrees of freedom and its dynamics remains unexplored. Here, we study the charge filling-dependent valley relaxation dynamics of interlayer excitons (IXs) in WSe2/WS2 moiré heterobilayer system. The evolution of moiré IXs dynamics across the Mott transition is elucidated by combining time-resolved optical spectroscopy with Monte Carlo simulation. Our results show that the radiative decay and recombination rate of IXs are enhanced at the integer filling factors n (=-1). Moreover, the valley relaxation rate of IXs at n=$\pm$1 is significantly decreased. The resulting reduction in wavefunction overlap and phonon scattering process suppresses the nonradiative recombination and intervalley scattering of IXs. These anomalous behaviors are attributed to the modification of IXs recombination pathways and enhance excitonic coherence due to the localization of introduced charge carriers at integer filling of moiré site. Our results explore exciton and valley dynamics as sensitive probes of strongly correlated states in moiré systems and highlight possible ways to control excitonic coherence and valleytronic properties in two-dimensional quantum materials.

cond-mat.mes-hall↗

arXiv2021

High resolution IR spectroscopy and imaging based on graphene micro emitters

IR spectroscopy such as Fourier transform infrared spectroscopy (FTIR) are widely used for the investigation of structure and the quantitative determination of substances in the fields of chemistry, physics, biology, medicine, and astronomy, because the energy of IR absorption corresponds to the energy for each vibrational transition in functional groups within molecules. Microscopic imaging of FTIR is used for various practical applications, as it enables visualization of the composition distribution and changes in molecular structure without fluorescent labels. However, FTIR microscopy with an objective lens has a diffraction limit causing the low spatial resolution with the order of 10 $μ$m. Here, we present high-spatial-resolution IR spectroscopy and imaging based on graphene micro-emitters, which have distinct features over conventional IR sources: a planar structure, bright intensity, a small footprint (sub $μ$m$^2$), and high modulation speed of ~100 kHz. We performed IR absorption spectroscopy on a polymer thin film using graphene micro-emitters, realizing high-resolution IR imaging with a spatial resolution of ~2 $μ$m, far higher than that of the conventional FTIR. We show the two-dimensional IR chemical imaging that visualizes the distribution of the chemical information, such as molecular species and functional groups. This technique can open new routes for novel IR imaging and microanalysis in material science, physics, chemistry, biology, and medicine.

physics.app-ph↗