Surviving spins in two dimensions

29 Feb 2016 NUS scientists have established the mechanisms for spin motion in molybdenum disulfide, an emerging two-dimensional (2D) material.

An atomically thin sheet of molybdenum disulfide (MoS2) is a new class of 2D material recognised for its potential for novel computing devices such as spin transistors. Despite its potential, little is known about the lifetime of electron spins – an important information carrier – in this system. A team co-led by Prof Goki EDA and Shaffique ADAM, in collaboration with experimental and theoretical research groups from the Department of Physics in NUS and Yale-NUS College, has discovered the underlying spin scattering mechanisms in a 2D sheet of MoS2. The work, performed as a collaboration between four research groups at the Centre for Advanced 2D Materials (CA2DM), a Singapore National Research Foundation (NRF) mid-sized centre, used highly precise measurements of the classical and quantum motion of electrons to extract information on how long spins live in this new material.

Mr Hennrik SCHMIDT, who at the time was a Research Fellow of Prof Eda said, “Establishing the mechanism for spin scattering paves the way for future spintronic devices.  Moreover, our method revealed the properties of the electron spins without resorting to invasive optical probes”.

Due to symmetry reasons, the dynamics of spins in MoS2 are uniquely associated with another degree of freedom called valley quantum number. The team aims to reveal the interplay between spin and valley dynamics in this class of materials. The researchers anticipate that such studies will help in developing strategies for manipulating these unique quantum degrees of freedom in practical device applications.

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Schematic illustration of a “spin-flipping” event in single-layer molybdenum disulfide. [Image credit: Leiqiang CHU]

Reference

Schmidt H, Yudhistira I, Chu L, Castro Neto AH, Özyilmaz B, Adam S, Eda G. “Quantum transport and observation of Dyakonov-Perel spin-orbit scattering in monolayer MoS2” Phys. Rev. Lett. 116, 046803 (2016).