National University of Singapore (NUS) physicists have developed a concept to induce and directly quantify spin splitting in two-dimensional materials
By using this concept, they have experimentally achieved large tunability and a high degree of spin-polarization in graphene. This research achievement can potentially advance the field of two-dimensional (2D) spintronics, with applications for low-power electronics.
Joule heating poses a significant challenge in modern electronics, especially in devices such as personal computers and smartphones. This is an effect that occurs when the flow of electrical current passing through a material produces thermal energy, subsequently raising the material’s temperature. One potential solution involves the use of spin, instead of charge, in logic circuits. These circuits can, in principle, offer low-power consumption and ultrafast speed, owing to the reduction or elimination of Joule heating. This has given rise to the emerging field of spintronics.
Graphene is an ideal 2D material for spintronics, due to its long spin diffusion length and long spin lifetime even at room temperature. Even though graphene is not inherently spin-polarized, it can be induced to exhibit spin-splitting behavior by placing it near magnetic materials. However, there are two main challenges. There is a lack of direct methods for determining the spin-splitting energy and a limitation in graphene’s spin properties and tunability.
A research team led by Professor Ariando from the Department of Physics, NUS, developed an innovative concept to directly quantify spin-splitting energy in magnetic graphene using the Landau fan shift. Landau fan shift refers to the shift of intercept when plotting linear fits of oscillation frequency with charge carriers, which is due to the splitting of energy levels of charged particles in a magnetic field. It can be used to study the fundamental properties of matter. Moreover, the induced spin-splitting energy can be tuned over a broad range by a technique called field cooling.
The observed high spin polarization in graphene, coupled with its tunability in spin-splitting energy, offers a promising avenue for the development of 2D spintronics for low-power electronics.
The findings have been published in the journal Advanced Materials.