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The integration of confined exciton and localized surface plasmon in a hybrid nanostructure has recently stimulated extensive interests. The mechanistic insights into the elusive exciton–plasmon interplay at the nanoscale are of both fundamental and applicable values. Herein, by taking a hybrid WSe2/CuFeS2 system as a prototype, in which the excitonic semiconductor WSe2 nanosheets are interfaced with the plasmonic semiconductor CuFeS2 nanocrystals to form a heterostructure, we design and perform an ultrafast dynamics study to glean information in this regard. Specifically, the band-alignment relationship between the two components enables the contrasting case studies in which the excitonic excited states of WSe2 are pre-selected to be on-/off-resonant with the plasmon band of CuFeS2. As revealed by the joint observations from steady-state absorption and photoexcitation-dependent/temperature-dependent femtosecond time-resolved transient absorption (fs-TA) spectroscopy, an effective energy transfer process occurs in this exciton–plasmon system where the energy donor (acceptor) is the excitonic WSe2 (plasmonic CuFeS2) and its efficiency is modulated by the exciton–plasmon coupling strength. Furthermore, as inferred from the temperature-dependent fs-TA analysis, the opening of such an energy-transfer channel turns out to take place during the early phase of plasmon decay (∼1 ps). In addition, the activation energy of energy transfer for a specific exciton-state-selected case is estimated (∼200 meV). This work provides a dynamics perspective to the plasmon semiconductor-involved exciton–plasmon interplay that features excited-state selectivity of exciton band and, hence, would be of guiding value for rational design and optimization of relevant applications based on exciton–plasmon manipulation. [ABSTRACT FROM AUTHOR]

The reported experimental data of the temperature dependence of the electrical conductivity, σ(T), the Seebeck coefficient, S(T), and the Hall coefficient, RH(T) on n-type PdxCu1−xFeS2 (x = 0, 0.005, 0.01, and 0.02) polycrystalline samples have been analyzed including not only free-electron conduction in the 1st and the 2nd conduction band minimum (CBM) but also hopping conduction in an impurity band. The hopping mechanisms have been identified through the analysis of the reduced local activation energy of the conductivity. The amphoteric nature of Pd impurity atoms is assumed: a part of the doped Pd atoms are assumed to substitute the Cu-sites to form single donor states PdCu, while the rest are assumed to substitute the Fe-sites to form compensating acceptor states PdFe. Treating the density-of-states effective mass of the 1st CBM and the static dielectric constant as common fitting parameters, simultaneous fits to the σ(T), S(T), and RH(T) data have been successfully performed. Through the fits, the concentrations of donors and acceptors together with the ionization energies of the donor levels have been deduced for each sample. It is revealed that the concentration ratio of PdCu:PdFe is about 1.5:1. [ABSTRACT FROM AUTHOR]