Strong Rashba-Edelstein Effect-Induced Spin–Orbit Torques in Monolayer Transition Metal Dichalcogenide/Ferromagnet Bilayers

Abstract

The electronic and optoelectronic properties of two-dimensional materials have been extensively explored in graphene and layered transition metal dichalcogenides (TMDs). Spintronics in these two-dimensional materials could provide novel opportunities for future electronics, for example, efficient generation of spin current, which should enable the efficient manipulation of magnetic elements. So far, the quantitative determination of charge current-induced spin current and spin-orbit torques (SOTs) on the magnetic layer adjacent to two-dimensional materials is still lacking. Here, we report a large SOT generated by current-induced spin accumulation through the Rashba-Edelstein effect in the composites of monolayer TMD (MoS or WSe)/CoFeB bilayer. The effective spin conductivity corresponding to the SOT turns out to be almost temperature-independent. Our results suggest that the charge-spin conversion in the chemical vapor deposition-grown large-scale monolayer TMDs could potentially lead to high energy efficiency for magnetization reversal and convenient device integration for future spintronics based on two-dimensional materials.

Prospects of spintronics based on 2D materials

“…and (3) of the extrinsic SOC of Bychkov‐Rashba type introduced by a transverse electric field . Besides those discussed earlier, proximity effect was also successfully demonstrated in graphene/YIG, graphene/Au, and WSe 2 /CoFeB bilayers . However, the effects of these ‘extrinsic’ SOC are moderate.…”

“…A large number of first‐principles calculations have been carried out to study SOC in various materials and they have shown that SOC can split degenerate energy bands, thus modifying the electronic band structures of the materials. Some of the 2D materials such as TMDs show large SOC . However, much work in the field of spin‐orbitronics have been done on bulk materials of heavy elements, such as Ta, W, Ir, Pt, Au, and Bi, due to their large SOC.…”

“…For better device performance, 2D materials/systems with heavy elements that possess ‘intrinsic’ large SOC effect are desirable. Layered TMDs, MoS 2 , WS 2 , WSe 2 , WTe 2 have been predicted to show high efficiencies of spin‐charge conversion. But they are semiconductors and their applications in spin‐orbitronics are limited because of the low mobility and high resistivity.…”

Van der Waals magnets: Wonder building blocks for two‐dimensional spintronics?

“…Existing experimental studies have exclusively focused on chemical vapor deposition‐grown or mechanically exfoliated TMDs, necessitating additional steps, such as vacuum breaking and physical transfer (onto a substrate), prior to ferromagnet (FM) deposition . These approaches cannot provide the cleanest interface at the atomic level, which is, however, a key factor for achieving large spin signals in relevant devices, such as 2D‐based MTJs as already discussed above.…”

“…[152][153][154][155][156] Existing experimental studies have exclusively focused on chemical vapor deposition-grown or mechanically exfoliated TMDs, necessitating additional steps, such as vacuum breaking and physical transfer (onto a substrate), prior to ferromagnet (FM) deposition. 148,157 These approaches cannot provide the cleanest interface at the atomic level, which is, however, a key factor for achieving large spin signals in relevant devices, 158,159 such as 2D-based MTJs as already discussed above. An MBE-based growth strategy in response to the above issue has been demonstrated, enabling wafer-scale TMDs with full coverage on substrate and contaminationfree FM/TMD interface.…”