Novel mechanisms for electromagnetic wave emission in the terahertz frequency regime emerging at the nanometer scale have recently attracted intense attention for the purpose of searching next-generation broadband THz emitters. Here, we report broadband THz emission, utilizing the interface inverse Rashba-Edelstein effect. By engineering the symmetry of the Ag/Bi Rashba interface, we demonstrate a controllable THz radiation (∼0.1-5 THz) waveform emitted from metallic Fe/Ag/Bi heterostructures following photoexcitation. We further reveal that this type of THz radiation can be selectively superimposed on the emission discovered recently due to the inverse spin Hall effect, yielding a unique film thickness dependent emission pattern. Our results thus offer new opportunities for versatile broadband THz radiation using the interface quantum effects.
We investigate the quasiparticle dynamics in the prototype heavy fermion CeCoIn5 using ultrafast optical pump-probe spectroscopy. Our results indicate that this material system undergoes hybridization fluctuations before full establishment of the heavy electron coherence, as the temperature decreases from ∼120 K (T † ) to ∼55 K (T * ). We reveal that the observed anomalous phonon softening and damping reduction below T * are directly associated with opening of an indirect hybridization gap. We also discover a distinct collective mode with an energy of ∼8 meV below 20 K, which may be the experimental evidence of the predicted unconventional density wave. Our observations provide critical informations for understanding the hybridization dynamics in heavy fermion materials.
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