Fig. 4: Microscopic origin of THz emission through defect engineering.
From: Defect-induced helicity dependent terahertz emission in Dirac semimetal PtTe2 thin films
a The transient THz waveforms of PtTe2 films with various in-vacuo annealing time under LCP and RCP at φ = 0o, respectively. b Hall curves of PtTe2 films with various in-vacuo annealing time under the perpendicular field at 5 K. The inset shows a schematic of Hall bar device structure. c The extracted CPGE amplitude from a and extracted VTe contribution from b as a function of the annealing time. The lines are drawn as guides for the eyes. The error bars of the CPGE amplitude and the VTe contribution indicate the uncertainties from the calculations of the difference between LCP and RCP and the fitting of the experimental results, respectively. The thickness of PtTe2 films is 18 nm. d–f Band structures and Berry curvatures of PtTe2 obtained within the home-made codes. DFT bands are fitted for the defect-free sample (Δδ = 0) in d and the defective samples with VTe concentration difference Δδ = 18% in e and Δδ = 22% in f between two Te atoms in the minimum model, respectively. The right panels in d–f show the x component of BCD (\({\varLambda }_{x}^{\Omega }\)) for the defect-free and defective samples, respectively. No BCD is found in the defect-free sample.
