Electron spin is an important degree of freedom which can complement or even replace charge in information storage and logic devices. For spin-based electronics, it is essential to have materials with large spin signals and long spin relaxation times at room temperature (RT). With respect to the material selection, spin functionality in semiconductors in particular offers new opportunities that are unfeasible in metal-based spintronics devices. However, the carrier concentrations in these bulk semiconductors are determined extrinsically with the addition of foreign atoms by ion implantation. This causes additional scattering, and masks their intrinsic properties.

In this respect 2D materials hold great promise due to the ability of tuning the carrier concentration by the electric field effect without modifying their intrinsic properties.  In this talk, I will discuss the electric field control of spin transport in 2D materials. First, 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 spin valves geometry with pure spin currents, spin relaxation times in BP can be as high as ~ 4ns with spin relaxation lengths exceeding 6 µm. These values are at least an order of magnitude higher than what has been measured in typical graphene and other metals based spin valves. After discussing the dominant spin relaxation mechanism in BP crystal, I will demonstrate that its spin transport properties can be manipulated in a transistor-like manner by just controlling the electric field even at RT. If the time permits, I will also present a similar electric field control effect in high mobility, dual-gated bilayer graphene spin valves.

About the Speaker: Dr Ahmet Avsar is an experimental condensed matter physicist specializing in the emerging fields of spintronics and two-dimensional crystals-based nanotechnology. Specifically, he studies the electron and spin transport in lithographically patterned, ultra- thin crystals based devices. He obtained PhD degree from Physics Department of National University of Singapore and he is currently a research fellow at Centre for Advanced 2D Materials, Singapore.