Tan Dao

Tan Dao

University of New Hampshire
McNair Scholar, 2019 & 2020
Major: Physics 
2020 Mentor: Dr. Jiadong Zang, Department of Physics
2020 Research Title: The Topological Hall Effect in Magnet Systems with Broken Inversion Symmetry 

The Topological Hall Effect in Magnet Systems with Broken Inversion Symmetry
Magnetic materials are crucial in the development of memory and data storage devices, aspolarized spins in magnets are being used to hold information. As technology advances, we needmore powerful data storage devices to store large amounts of information. Magnetic skyrmion isa great candidate for future memory devices due to its nanoscale structure and topologicallyrobustness. So far, the best transport signature of the magnetic skyrmions is the so-calledtopological Hall effect, in which electrons move sideways traversing skyrmions. However, thephenomenon of the topological Hall effect might have originated from other mechanisms. Inparticular, a giant topological Hall effect was reported in transition metal oxides, but thepresence of skyrmions therein remains elusive. Therefore, a new model to explain themechanism for the topology Hall effect is of urgent need, and the transport footprint ofskyrmions must be unequivocally identified. Here, working with Prof. Zang from the physicsdepartment, I propose to theoretically model skyrmion materials in the presence of non-magneticimpurities, and employ high-performance numerical simulations to characterize the topologicalHall effect therein. Fully understanding the mechanism for the topological Hall effect willsolidify our understanding of the magnetic skyrmions and opens up many exciting applications.

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2019 Mentor: Dr. Shawna Hollin, Department of Physics 
2019 Research Title: The Effects Of Strain  And Suspension On The Electronic Properties Of Molybdenum Disulfide

The Effects Of Strain And Suspension On The Electronic Properties Of Molybdenum Disulfide
We live in an age where small, lightweight, and strong materials are necessary for our future development of electronics. Two-dimensional materials can fill this need because they are as thin as physically possible and have tunable electronic properties that can be used for development of flexible, faster, and smaller electronic devices. One of the most exciting two-dimensional materials is molybdenum disulfide (MoS2). Single layer MoS2 exhibits a tunable band gap and tunable electrical conductivity when a local strain, stretching between atoms, is induced. The ability to tune bandgap and electrical conductivity is important for making electronics with faster computation speed and lower power consumption. To tune the electronic properties by using strain, we first need to establish a better understanding between strain and electronic properties. For this Mc- Nair summer research, I propose to build on my 2019 spring URA work to characterize the local conductivity in single-to-few layer strained and suspended MoS2 sheets. I will be making MoS2 device on an insulating substrate with nanopatterned valleys and hills by using the Transmission Electron Microscopy (TEM) grids to make micro-electrical connections, and then use conductive atomic force microscopy (C-AFM) to characterize the local electrical conductivity at the nanoscale level. This study will determine whether strain can cause variations in the conductivity and how they are related. The results of this study will help connect the fundamental understanding between mechanical properties and electronic properties, which can be used to develop smaller, faster, and lower energy consumption electronics.

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