Unveiling of Terahertz Emission from Ultrafast Demagnetization and the Anomalous Hall Effect in a Single Ferromagnetic Film

Abstract

Using terahertz emission spectroscopy, we investigate the elementary spin dynamics in ferromagnetic Fe single layer on a sub-picosecond timescale. We demonstrate that THz radiation changes its polarity with reversal of the magnetization applied by the external magnetic field. In addition, it is found that the sign of THz polarity excited from different sides, is defined by the thickness of Fe layer and Fe/dielectric interface. Based on the thickness and symmetry dependences of THz emission, we experimentally distinguish between the two major contributions: ultrafast demagnetization (UDM) and anomalous Hall effect (AHE). Our expermental results not only enrich the understanding of THz electromagnetic generation induced by femtosecond laser pulse, but also provide a practical way to access the laser-induced ultrafast spin dynamics in magnetic structures.

Comprehensive study of the ultrafast photoexcited carrier dynamics in Sb2Te3–GeTe superlattices

“…[25][26][27] On one hand, since the nonequilibrium distribution of photoexcited carriers causes the transient currents and subsequently generates the THz radiation, [28][29][30] THz emission spectroscopy has been proven to be a good method for investigating the transient carrier transport properties in symmetry-broken materials, such as ferromagnetic superlattices, transition metal dichalcogenides, strongly correlated and topological materials. [31][32][33][34] On the other hand, transient reflectance spectroscopy is a powerful technique to investigate bandgap renormalization, Pauli blocking and free carriers' absorption, providing an understanding of excited-state carrier dynamics in topological materials. [35,36] In this paper, we combine THz emission spectroscopy and transient reflectance spectroscopy to investigate the ultrafast current and carrier dynamics in Sb 2 Te 3 -GeTe superlattices.…”