Fig. 1: THz emissions from Cd3As2 epitaxial film with a thickness gradient.
From: Ultrafast photothermoelectric effect in Dirac semimetallic Cd3As2 revealed by terahertz emission
a The position of a cut piece (white dash line region) in an as-grown wafer, and the mapping of relative thickness of the Cd3As2 film determined by two-dimensional scanning of laser transmittance. The blue circle marks the excitation laser spot and the arrow illustrates the direction of thickness gradient on the spot. b Schematic diagram of experimental setup, where θ denotes the azimuthal angle of the sample with respect to y-axis. Inset: the crystal structure of Cd3As2 along (112) plane. c Schematic diagram of THz emissions from transient current generated by 800-nm optical excitation. EN and E// here denote the instantaneous electrical field of THz emission from Nernst current (JN) under magnetic field and from the in-plane current (J//), respectively. J⊥ denotes the out-of-plane current. d Typical THz waveform generated by J//, J⊥ and JN in (c). The two THz waveforms from J⊥ and JN are obtained by sample tilting and by applying an in-plane magnetic field respectively.
