High Spin Hall Conductivity in Large‐Area Type‐II Dirac Semimetal PtTe₂

Abstract

Spin-orbit torque (SOT) provides an ultrafast and energy-efficient means to switch magnetization, which is of fundamental and technical importance for spintronic devices. [1][2][3][4][5] A typical SOT device consists of heavy metal/ferromagnet (HM/FM) bilayer, where the HM (e.g., Pt, W, Ta, etc.) converts charge current into spin current mainly due to the spin Hall effect (SHE) and then exerts a torque on the adjacent FM enabling magnetization manipulation. To improve the energy efficiency of SOT-driven magnetization switching, considerable efforts have been made to enhance the charge-spin conversion efficiency of HM [6][7][8][9] and reduce the shunting current in the FM. [10,11] Engineering the bilayer structure [9,12] or replacing HM by novel materials with larger charge-spin conversion efficiency and higher conductivity [10,13,14] are possible avenues to realize higher SOT efficiency. Manipulation of magnetization by electric-current-induced spin-orbit torque (SOT) is of great importance for spintronic applications because of its merits in energy-efficient and high-speed operation. An ideal material for SOT applications should possess high charge-spin conversion efficiency and high electrical conductivity. Recently, transition metal dichalcogenides (TMDs) emerge as intriguing platforms for SOT study because of their controllability in spin-orbit coupling, conductivity, and energy band topology. Although TMDs show great potentials in SOT applications, the present study is restricted to the mechanically exfoliated samples with small sizes and relatively low conductivities.Here, a manufacturable recipe is developed to fabricate large-area thin films of PtTe 2 , a type-II Dirac semimetal, to study their capability of generating SOT. Large SOT efficiency together with high conductivity results in a giant spin Hall conductivity of PtTe 2 thin films, which is the largest value among the presently reported TMDs. It is further demonstrated that the SOT from PtTe 2 layer can switch a perpendicularly magnetized CoTb layer efficiently. This work paves the way for employing PtTe 2 -like TMDs for wafer-scale spintronic device applications.

Large Damping-Like Spin–Orbit Torque in a 2D Conductive 1T-TaS2 Monolayer

“… 17 − 19 The quantitative estimation of the SHC and auto-oscillations current density in our TaS 2 /Py hold valuable information for several spintronic applications. Evidently, the interface of our TaS 2 /Py bilayer, as confirmed by cross-sectional TEM and supported by parameters extracted from X-ray reflectivity measurements, is clean in contrast to other works using exfoliated sheets and nonuniform growth where extrinsic contributions from strain and defect-related issues 17 , 48 , 38 reduce the charge-spin conversion efficiency. First-principles calculations based on the density functional theory (DFT) reveal the role of SOC for lifting the degeneracy in the band structure of TaS 2 /Py.…”

Wafer‐scale vertical van der Waals heterostructures

“…191,192 Hence, modifying the metalsemiconductor contact interface is an effective strategy to improve device performance. Specifically, using metallic 2D materials (graphene, 193 some 1 T phase TMDs 47,187,[194][195][196][197] ) as electrodes for (opto)electronics through epitaxy growth 35 or phase transition 198,199 will alleviate the pining effect. In addition, transferring the prefabricated metal electrodes can also avoid creating defects and strains, resulting in an atomically sharp and near perfect metal/2D semiconductor interface.…”

Spin-Orbit Torques in Transition Metal Dichalcogenide/Ferromagnet Heterostructures

“…Comparing the TMDs in this way allows us to pinpoint important differences and similarities in the observed torques. (Xu et al, 2020) PtTe 2 (3-20 nm) CVD Py (2.5, 5.0, 7.5, 10 nm)…”

“…More recently, PtTe 2 /Py devices (Xu et al, 2020) have shown a high spin-torque conductivity for the in-plane DL torque σ y e 1.6 × 10 5 (Z/2e)(Ωm) − 1 . This value is one order of magnitude (or larger) than the values encountered in other TMD-based devices and comparable to devices based on heavy-metal or topological-insulators.…”