Ultrafast Spin‐Charge Conversion at SnBi₂Te₄/Co Topological Insulator Interfaces Probed by Terahertz Emission Spectroscopy

Abstract

Spin‐to‐charge conversion (SCC) involving topological surface states (TSS) is one of the most promising routes for highly efficient spintronic devices for terahertz (THz) emission. Here, the THz generation generally occurs mainly via SCC consisting in efficient dynamical spin injection into spin‐locked TSS. In this work, sizable THz emission from a nanometric thick topological insulator (TI)/ferromagnetic junction—SnBi2Te4/Co—specifically designed to avoid bulk band crossing with the TSS at the Fermi level, unlike its parent material Bi2Te3 is demonstrated. THz emission time domain spectroscopy (TDS) is used to indicate the TSS contribution to the SCC by investigating the TI thickness and angular dependence of the THz emission. This work illustrates THz emission TDS as a powerful tool alongside angular resolved photoemission spectroscopy (ARPES) methods to investigate the interfacial spintronic properties of TI/ferromagnet bilayers.

Spin‐Momentum Locking and Ultrafast Spin‐Charge Conversion in Ultrathin Epitaxial Bi1 − xSbx Topological Insulator

“…[22][23][24] BiSb therefore has considerable potential as candidate for spintronics applications as well as for recently engineered efficient spintronic THz emitters. [25][26][27][28][29][30][31][32] In this letter, we report on our detailed investigation of the surface state SML properties of ultrathin (1 1 1)-oriented Bi 1 − x Sb x epitaxial films. They exhibit a topological phase as recently confirmed by our angular-resolved photo-emission spectroscopy (ARPES) measurements.…”

Passivation of Bi2Te3 Topological Insulator by Transferred CVD‐Graphene: Toward Intermixing‐Free Interfaces

“…[4] However, to identify the microscopic mechanism of CSI and SOTs, as well as to maximize their efficiency, a deep understanding of the properties of the TI/FM interface is needed. [5][6][7][8][9][10][11] Interface phenomena are complex, involving charge transfer, hybridization, intermixing, or alloying. More so when airsensitive or reactive elements are involved, in which case, oxidation and intermixing are particularly relevant.…”

“…[ 4 ] However, to identify the microscopic mechanism of CSI and SOTs, as well as to maximize their efficiency, a deep understanding of the properties of the TI/FM interface is needed. [ 5–11 ]…”

Magnetization rotation-based polarization control of spintronic terahertz emitter

“…[6][7][8] In contrast to these traditional methods, only spintronic terahertz emitters utilize the spin of electrons to generate terahertz radiation. 9,10 The substantial advantage is a 30-THz broadband gapless spectrum, not needing extreme optical pulse energies as plasma. 6 The spintronic emitters consist of a few nanometers thick metallic layers, which makes them easy to fabricate, inexpensive, and mechanically and thermally durable.…”