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We have measured the terahertz responses of plasmon-phonon interaction in the topological insulator Bi2Se3 metamaterials. Upon photoexcitation, we observed transient phonon stiffening of ∼0.1 THz when the plasmon frequency is above the phonon energy.
We report the first anisotropic two excitons dynamics in bulk ReS2. Both exciton states show anisotropic dynamics upon carrier injection with a stronger response in higher exciton state (X2) than the lower state (X1).
We present ultrafast optical Stark effect of anisotropic excitons in few layer ReS2. With varying pump-probe polarization configuration, we selectively shift the excitons, based on their anisotropic optical selection rules.
We demonstrate infrared photodetectors based on graphene-Bi2Se3 heterostructures with high responsivity (≥1.9 A/W) at room temperature. Strong photogating effect across the tunneling barrier and built-in potential enables the internal quantum efficiency larger than 100 %.
We reported terahertz plasmon modulation in topological insulators by directly patterning Bi2Se3 thin films. Changing the dimension of Bi2Se3 microslits, we observed the destructive interference between terahertz plasmon and bulk phonon.
We introduce a new methodology for controlling ultrafast plasmon-phonon interaction using topological phase transition. This is based on the manipulation of the spatial overlap between topological surface plasmonic states and bulk phonon.
We report new tunable Fano interference phenomena depending on topological phase in (Bi1−xInx)2Se3. The controlled spatial overlap of topological surface wavefunction with bulk phonon is responsible for the ultrafast tunability of the Fano resonance.
We report the first ultrafast mid-infrared (IR) spectroscopy in monolayer MoS2. The observed mid-IR dynamics show multiple, yet broadened absorption, indicating the predominant intraexcitonic transition from the ground to the higher-lying excitonic states.
We report the first measurement of ultrafast mid-infrared (IR) spectroscopy in monolayer MoS2. The observed mid-IR dynamics shows large photo-excited absorption, indicating the predominant intraexcitonic transition from the ground to the higher-lying excitonic states.
We present ultrafast optical studies of the Dirac surface dynamics in a topological insulator Bi2Se3 via optical pump mid-infrared probe spectroscopy. We observed largely enhanced carrier relaxation when the topological-phase transition takes place.
We present ultrafast optical modulation of plasmons in a topological insulator Bi2Se3 micrio-ribbon array. Unprecedented giant modulation depth up to 2,400 % is obtained with very low fluence of optical control pulse.
We present ultrafast terahertz scattering dynamics in topological insulator Bi2Se3 thin films. Upon photoexcitation, the surface-scattering rate is increased, resulting in decrease of conductance. At high temperature, however, the photo-generated electrons suppress the surface-scattering.
We study the time- and spectrally-resolved exciton dynamics of a few-layer molybdenum disulfide using ultrafast optical pump-probe spectroscopy. We find that the carrier induced broadening significantly influence on the band-edge transmission spectra even with small carrier densities.
We present direct experimental measurement of exciton-exciton annihilation as fast photo-bleaching at exactly twice the lowest exciton energy in individually isolated single-walled carbon nanotubes. Exciton-exciton scatterings were rigorously identified by determining the 1s-2p transition using ultrafast mid-infrared intra-excitonic spectroscopy.
We present terahertz carrier dynamics in individual silicon nanowires by ultrafast optical-pump and terahertz-probe spectroscopy. Density-dependent study reveals that the surface traps play a major role in the carrier dynamics, in which the conductivity changes with the terahertz polarization parallel to nanowire axis are extracted.
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