Generation and Control of Terahertz Spin Currents in Topology‐Induced 2D Ferromagnetic Fe₃GeTe₂|Bi₂Te₃ Heterostructures

Abstract

Future information technologies for low‐dissipation quantum computation, high‐speed storage, and on‐chip communication applications require the development of atomically thin, ultracompact, and ultrafast spintronic devices in which information is encoded, stored, and processed using electron spin. Exploring low‐dimensional magnetic materials, designing novel heterostructures, and generating and controlling ultrafast electron spin in 2D magnetism at room temperature, preferably in the unprecedented terahertz (THz) regime, is in high demand. Using THz emission spectroscopy driven by femtosecond laser pulses, optical THz spin‐current bursts at room temperature in the 2D van der Waals ferromagnetic Fe3GeTe2 (FGT) integrated with Bi2Te3 as a topological insulator are successfully realized. The symmetry of the THz radiation is effectively controlled by the optical pumping incidence and external magnetic field directions, indicating that the THz generation mechanism is the inverse Edelstein effect contributed spin‐to‐charge conversion. Thickness‐, temperature‐, and structure‐dependent nontrivial THz transients reveal that topology‐enhanced interlayer exchange coupling increases the FGT Curie temperature to room temperature, which provides an effective approach for engineering THz spin‐current pulses. These results contribute to the goal of all‐optical generation, manipulation, and detection of ultrafast THz spin currents in room‐temperature 2D magnetism, accelerating the development of atomically thin high‐speed spintronic devices.

Transient THz Study of Phonon-Assisted Carrier Scattering between Bulk and Surface States in Bi2Te3

“…Figure b shows the Raman spectrum of Bi 2 Te 3 in the range 40–200 cm –1 . The peaks around 63.5, 136.0, and 102.8 cm –1 correspond to out-of-plane vibrational modes A 1g 1 and A 1g 2 and the in-plane vibrational mode E g , respectively, which are consistent with the reports in literature. , Figure c shows the XRD pattern, showing a high c -axis orientation and no characteristic peaks of other orientations. , Both Raman spectra and XRD patterns demonstrate the high quality of the Bi 2 Te 3 nanocrystal film.…”

“…22,23 Figure 1c shows the XRD pattern, showing a high c-axis orientation and no characteristic peaks of other orientations. 24,25 Both Raman spectra and XRD patterns demonstrate the high quality of the Bi 2 Te 3 nanocrystal film.…”

Interlayer Phonon Coupling from Heavy and Light Sublayers in a Natural Van der Waals Superlattice

“…Nonetheless, in some cases, van der Waals (vdW) forces can still influence interlayer interactions through subtle energy fluctuations, impacting more nuanced and complicated interlayer properties. For example, in vdW superlattices, the interaction between fundamental particles exhibits a greater degree of diversity compared to traditional vdW layered materials, which arises from the extra competition between different chemical potentials of sublayers and relatively weak interlayer interactions, resulting in a variety of emerging phenomena, such as Moiré excitons, 2D superconductivity, magnetic exchange interactions, , long-lifetime interlayer excitons, and topological states …”

High Efficiency and Flexible Modulation of Spintronic Terahertz Emitters in Synthetic Antiferromagnets

“…The parameter of the spin Hall angle θ SH reflects the spin-to-charge conversion efficiency of the NM layer, which is related to the spin–orbit coupling interaction. − Apparently, the NM layer plays a key role in the laser-excited THz emission process, and materials with a high θ SH are expected. Various NM layer materials with strong spin–orbit coupling, such as nonmagnetic heavy metals, − antiferromagnets, − two-dimensional materials, − and topological insulators, − have been experimentally demonstrated to be able to generate strong THz signals. − The THz emission process in STEs is complex and involves various successive effects including spin generation, spin diffusion, spin decoherence, and spin–charge conversion. The layer structure and film quality also play a crucial role in determining the efficiency of THz emission. ,− Beigang et al have conducted investigations in Fe/Pt bilayers to understand the different roles of layer thickness, growth condition, substrate choice, and geometrical arrangement in the THz emission process based on the ISHE-based mechanism.…”