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Abstract
 

Electron spin is an important degree of freedom which can complement charge in information storage and logic devices. With respect to the material selection for spintronics, two-dimensional (2D) materials and their van der Waals heterostructures offer new opportunities that are unfeasible in bulk materials. In this talk, I will first discuss basics of graphene spintronics¹ and our attempts for solving its major issues. These advancements include spin lifetimes enhancement of graphene spin valves², nondestructive optical spin injection in order to eliminate contact induced spin dephasing effects³ and enhancement of its very weak spin orbit coupling strength by utilizing proximity effect in order to create opportunities for the manipulation of spin current⁴. These have been achieved by creating artificial interfaces with other 2D crystals such as boron nitride (h-BN) and transition metal dichalcogenides (TMDCs). Then, I will discuss our recent spin transport measurements performed in 2D semiconductor materials. I will introduce ultra-thin, semiconducting black phosphorus (BP) as a promising material for possible spintronics applications requiring rectification and amplification actions. Based on measurements in the non-local geometry with pure spin currents, spin relaxation times in h-BN encapsulated BP spin valves can be as high as ~ 4 ns with spin relaxation lengths exceeding 6 µm⁵. I will demonstrate that its spin transport properties can be manipulated in a transistor-like manner by just controlling the electric field even at room temperature thanks to its semiconducting nature. If the time permits, I will discuss our recent quantum transport measurements probing the spin/valley dynamics at the conduction and valance bands of monolayer TMDCs⁶. Finally I will provide my perspective about 2D spintronics.

1. Avsar, A. et al. Toward wafer scale fabrication of graphene based spin valve devices. Nano Lett. 11, 2363–8 (2011).
2. Avsar, A. et al. Electronic spin transport in dual-gated bilayer graphene. NPG Asia Mater. 8, e274 (2016).
3. Avsar, A. et al. Optospintronics in graphene via proximity coupling. ACS Nano acsnano.7b06800 (2017).
4. Avsar, A. et al. Spin-orbit proximity effect in graphene. Nat. Commun. 5, 4875 (2014).
5. Avsar, A. et al. Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes. Nat. Phys. 13, 888–893 (2017).
6. Marinov, K., Avsar, A., Watanabe, K., Taniguchi, T. & Kis, A. Resolving the spin splitting in the conduction band of monolayer MoS₂. Nat. Commun. 8, 1938 (2017).

Anyone interested is welcome to attend.