Circular Photogalvanic Current in Ni-Doped CdAs Films Epitaxied on GaAs(111)B Substrate.

Magnetic element doped CdAs Dirac semimetal has attracted great attention for revealing the novel quantum phenomena and infrared opto-electronic applications. In this work, the circular photogalvanic effect (CPGE) was investigated at various temperatures for the Ni-doped CdAs films which were grown on GaAs(111)B substrate by molecular beam epitaxy. The CPGE current generation was found to originate from the structural symmetry breaking induced by the lattice strain and magnetic doping in the Ni-doped CdAs films, similar to that in the undoped ones.

Ultrafast Optical Probe of Coherent Acoustic Phonons in Dirac Semimetal CdAs Film Epitaxied on GaAs(111)B Substrate.

Coherent longitudinal acoustic phonon (CAP) generation in epitaxial Dirac semimetal CdAs films with different thicknesses was investigated by a time-resolved reflectance technique. The short-lived weak CAP oscillations can be observed only in the thicker CdAs films, and their central frequency of 0.039 THz has no dependence on sample thickness, but is nearly inversely proportional to the probe wavelength.

Strain-induced circular photogalvanic current in Dirac semimetal CdAs films epitaxied on a GaAs(111)B substrate.

Dirac semimetal (DSM) CdAs has drawn great attention for exploring the novel quantum phenomena and high-speed optoelectronic applications. The circular photogalvanic effect (CPGE) current, resulting from the optically-excited spin orientation transport, was theoretically predicted to vanish in an ideal Dirac system due to the symmetric photoexcitation about the Dirac point. Here, we reported the observation of the CPGE photocurrent in epitaxial CdAs thin films grown on a GaAs(111)B substrate.

Tunable Room-Temperature Ferromagnetism in Two-Dimensional CrTe.

The manipulation of magnetism provides a unique opportunity for the development of data storage and spintronic applications. Until now, electrical control, pressure tuning, stacking structure dependence, and nanoscale engineering have been realized. However, as the dimensions are decreased, the decrease of the ferromagnetism phase transition temperature () is a universal trend in ferromagnets.

Photo-excited carrier relaxation dynamics in two-dimensional InSe flakes.

Carrier relaxation dynamics of InSe flakes is investigated by using time-resolved pump-probe reflectivity measurement. The photocarriers associated with the P orbital band-edge transition at 2.40 eV, which is coupled to the in-plane polarized light, is observed to possess a lifetime of ∼19 ps at room temperature and ∼99 ps at 10 K.

Ultrafast Dynamics of Spin Generation and Relaxation in Layered WSe.

We investigated the build-up and relaxation processes of spin-polarized A- and B-exciton dynamics in monolayer, bilayer, and bulk WSe using helicity-resolved two-color pump-probe spectroscopy. Substantial spin polarization was confirmed in bulk crystals, though the spin polarization degree of A excitons decreased from monolayer to bulk. However, the spin polarization of A excitons almost vanished in all different layered-flakes when resonantly pumping the B-exciton transition, owing to the dominant role of interexciton transfer.