The bandgap, electrical, and optical properties of PtSe2 depend dramatically on the vertical stacking and fabrication method. Here, we study the nonlinear absorption properties of the PtSe2 films composed of both semiconducting and semimetallic phases in a single film. These PtSe2 films exhibit remarkable thickness-dependent saturable absorption for femtosecond pulses at 400 nm and 800 nm. The saturation intensities decrease with the increase in the film thickness due to the accompanied increase in the semimetallic component and are much smaller than the reported values of PtSe2 synthesized by thermally assisted conversion. The saturable absorption characteristics are confirmed by time-resolved spectroscopies. The nonlinear refractive indexes of these PtSe2 films should be smaller than 1 × 10–12 cm2/W. Our results imply that the optical nonlinearities of PtSe2 could be flexibly tuned by the synthesis method and thickness.

The temperature evolution of icosahedral medium-range order formed by interpenetrating icosahedra in CuZr metallic glassforming liquids was investigated via molecular dynamics simulations. Scaling analysis based on percolation theory was employed, and it is found that the size distribution of clusters formed by the central atoms of icosahedra at various temperatures follows a very good scaling law with the cluster number density scaled by S−τ and the cluster size S scaled by |1 − Tc/T|−1/σ, respectively. Here Tc is scaling crossover-temperature. τ and σ are scaling exponents. The critical scaling behaviour suggests that there would be a structural phase transition manifested by percolation of locally favoured structures underlying the glass transition, if the liquid could be cooled slowly enough but without crystallization intervening. Furthermore, it is revealed that when icosahedral short-range order (ISRO) extends to medium-range length scale by connection, the atomic configurations of ISROs will be optimized from distorted ones towards more regular ones gradually, which significantly lowers the energies of ISROs and introduces geometric frustration simultaneously. Both factors make key impacts on the drastic dynamic slow-down of supercooled liquids. Our findings provide direct structure-property relationship for understanding the nature of glass transition.

We investigate the photoexcited–carrier dynamics and coherent acoustic phonon oscillations in mechanically exfoliated PdSe2 flakes with a thickness ranging from 10.6 nm to 54 nm using time-resolved transient reflection spectroscopy.

Tunable optical properties could expand the functionalities of optoelectronic devices, exploring materials with tunable optical properties is important for the development of high-performance optoelectronic devices. CuInP2S6 (CIPS) is a ferroelectric...

As one of the representatives of emerging metallic transition-metal dichalcogenides, niobium ditelluride (NbTe2) has attracted intensive interest recently due to its distorted lattice structure and unique physical properties. Here, we report on the ultrafast carrier dynamics in NbTe2 measured using time-resolved pump–probe transient reflection spectroscopy. A thickness-dependent carrier relaxation time is observed, exhibiting a clear increase in the fast and slow carrier decay rates for thin NbTe2 flakes. In addition, pump-power-dependent measurements indicate that the carrier relaxation rates are power-independent and the peak amplitude of the transient reflectivity increases linearly with the pump power. The isotropic relaxation dynamics in NbTe2 is also verified by performing polarization-resolved pump–probe measurements. These results provide insight into the light–matter interactions and charge-carrier dynamics in NbTe2 and will pave the way for its applications to photonic and optoelectronic devices.