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Promising 2D material opens path for next-gen spintronics

Posted: 03 Feb 2016 ?? ?Print Version ?Bookmark and Share

Keywords:National University of Singapore? spintronics? 2D material? MoS2? transistor?

A research team from the National University of Singapore (NUS) and Yale-NUS College has laid down the mechanisms for spin motion in molybdenum disulphide (MoS2), an emerging 2D material. According to the team, their discovery answers a research question on the properties of electron spin in single layers of 2D materials and paves the way for the next generation of spintronics and low-power devices.

MoS2, a class of transition metal dichalcogenide compounds, has attracted great attention due to wide recognition of its potential for manipulating novel quantum degrees of freedom such as spin and valley. Due to its unique material properties, a single layer of MoS2 has the potential to be used for spin transistors, where both electric current and spin current can be switched on and off independently. Despite this potential for application, there have not been any experimental studies on the mechanism for spin dynamics in MoS2.

To address this gap, scientists from the Centre for Advanced 2D Materials at NUS used highly precise measurements of the classical and quantum motion of electrons to extract information on how long spins live in this new material.

MoS2

The sketch shows scattering in the two valleys of MoS2 close to the conduction band by spin-orbit and intervalley scattering. While the first flips the spin orientation, the second changes valley with preserved spin. Very different scattering times result in the observed transition of weak antilocalisation to weak localisation as experimentally observed in the magnetoresistance as function of temperature and magnetic field (right).

The team of scientists led by assistant professor Goki Eda, co-leader of this study who is from the NUS Department of Physics and Department of Chemistry, thinned down a crystal of molybdenite, a mineral of MoS2, to less than 1nm. Here, the electrons live in a purely 2D plane that is just one atom thick. The researchers then successfully injected a high density of electrons in this ultra-thin material to enable measurements in the quantum mechanical regime. Quantum transport measurements at low temperatures of 271C revealed a surprising transition, where quantum mechanical wave interference switched from constructive to destructive with increasing magnetic field.

Indra Yudhistira, a research associate with the NUS department of physics who is under the supervision of assistant professor Shaffique Adam, co-leader of the NUS study who is from Yale-NUS College and NUS department of physics, demonstrated that this crossover was caused by spin dynamics.

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