Cheng Tan on Award night with Marie and Graeme Snook

Cheng Tan - Winner 2019 Ian Snook Prize

Cheng Tan describes his 3 publications below. 

My research during PhD mostly focuses on two-dimensional van der Waals (vdW) materials. They are potential building blocks for new, high-performance electronic, electro-optic, and photonic devices. However, their application in spintronics has been limited because so few materials display the required magnetic properties. For serious consideration in spintronics, a vdW ferromagnetic metal with hard magnetic properties and a near square-shaped hysteresis loop is indispensable. Perpendicular magnetic anisotropy is also favourable. In 2017, 2 groups demonstrate the existence of 2D ferromagnetism on two 2D materials-CrI3 and Cr2Ge2Te6. However, both of them are insulators (or semiconductors). For the 2D VdW spintronics, a metallic vdW ferromagnetic material is essential. Then we performed the electron transport on a 2D material Fe3GeTe2 (FGT) and demonstrated that the material is very ideal for the vdW spintronics. This work published a NatureCommunications.

Then we utilize the FGT to explore the vdW spintronics. I firstly developed the vdW heterostructure stacking technique in our lab.. This technique enables the manual fabrication of heterostructures. We firstly exfoliate the thin nanoflakes on the substrate. Then we choose the thin and smooth nanoflakes. At last we pick up one layer by one layer and achieve the heterostructure.  We firstly fabricated  FGT/graphite/FGT vdW heterostructures and observed a rare phenomenon -- asymmetric magnetoresistance. By the following experiments and theoretical calculation, we confirm this is generated by the spin current on the FGT/graphite interlayer (actually here the current direction and the spin direction is coupled, which is the so-called  spin-momentum locking). This work we published the ScienceAdvances.

And the final paper is a small paper (OpticalMaterials) I finished in my first year when we have no instruments to do the work. My supervisor came in late 2014 and I arrive in Sep 2015. When I came, there’s nothing in the lab.. The material in this paper is WTe2, which had been predicted as topological insulator (only monolayer WTe2) and Weyl semimetal at that time. For this project we bought a WTe2 single crystal and exfoliated a crystal sheet, fabricating some nanogratings on the crystal sheet and checked the plasmon signal it can generate. More work can be done on this one such as the a real opto-electronic device, which is potential for application. The optical part we get a new postdoc to focus on it.    

Chengs Report

Cheng says the Ian Snook PhysicW Prize relieved the financial pressure he was experiencing and encouraged him to continue his studies. Cheng says when he received the prize he was “focusing on a tough new project and struggling mentally” and that the support of the Snook’s evoked his “determination and confidence to overcome difficulties”. Cheng hopes to continue his research, particularly around novel spintronic devices.

My great gratitude to Mrs. Marie Snook and Dr. Graeme Snook. The prize really encouraged and helped me greatly with my life and research. I should also give my highest respect and gratitude to Late Prof. Ian Snook.