Engineering topics

Tang, Jinke

Publications and source records attributed to Tang, Jinke.

5 records

DOE OSTI2024

Tunneling current-controlled spin states in few-layer van der Waals magnets

Abstract Effective control of magnetic phases in two-dimensional magnets would constitute crucial progress in spintronics, holding great potential for future computing technologies. Here, we report a new approach of leveraging tunneling current as a tool for controlling spin states in CrI 3 . We reveal that a tunneling current can deterministically switch between spin-parallel and spin-antiparallel states in few-layer CrI 3 , depending on the polarity and amplitude of the current. We propose a mechanism involving nonequilibrium spin accumulation in the graphene electrodes in contact with the CrI 3 layers. We further demonstrate tunneling current-tunable stochastic switching between multiple spin states of the CrI 3 tunnel devices, which goes beyond conventional bi-stable stochastic magnetic tunnel junctions and has not been documented in two-dimensional magnets. Our findings not only address the existing knowledge gap concerning the influence of tunneling currents in controlling the magnetism in two-dimensional magnets, but also unlock possibilities for energy-efficient probabilistic and neuromorphic computing.

Science & Technology - Other Topics↗

DOE OSTI2024

Investigation of topologically trivial and non-trivial spin textures and their relationships with the topological Hall effect

This proposal has two main goals: (1) to investigate ways to create a variety of spin textures, both topologically trivial and non-trivial, and (2) to establish the relationships between the created spin textures and the topological Hall effect (THE) signal. The approach is achieved by utilizing the van der Waals (vdW) two-dimensional (2D) magnetic materials, such as CrX 3 (X=I, Br, and Cl) and Fe 3 GeTe 2 , transferred onto various substrates with different interactions to create a wide range of spin textures; and utilize Spin helical system, such as Eu metal, and the impact of the thickness.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Environmentally Friendly Production of High-Quality and Multifunctional Carbon Quantum Dots from Coal

Researchers from the University of Wyoming and the University of Utah worked jointly to study the valorization of coal to carbon quantum dots (CQDs), a value-added product with a broad spectrum of applications. The CQDs were produced by an environmentally facile hydrothermal method, and the experimental factors influencing the properties of CQDs were investigated. We subsequently explored the applications of CQDs as co-sensitizers of dye-sensitized solar cells (DSSC) and photocatalysts of water treatment. As an outlook, techno-economic and environmental analysis studied the feasibility of mass production of CQDs.

01 COAL, LIGNITE, AND PEAT↗

DOE OSTI2023

Nonvolatile Memristive Effect in Few-Layer CrI 3 Driven by Electrostatic Gating

The potential of memristive devices for applications in nonvolatile memory and neuromorphic computing has sparked considerable interest, particularly in exploring memristive effects in two-dimensional (2D) magnetic materials. However, the progress in developing nonvolatile, magnetic field-free memristive devices using 2D magnets has been limited. In this work, we report an electrostatic-gating-induced nonvolatile memristive effect in CrI 3 -based tunnel junctions. The few-layer CrI 3 -based tunnel junction manifests notable hysteresis in its tunneling resistance as a function of gate voltage. We further engineered a nonvolatile memristor using the CrI 3 tunneling junction with low writing power and at zero magnetic field. We show that the hysteretic transport observed is not a result of trivial effects or inherent magnetic properties of CrI 3 . We propose a potential association between the memristive effect and the newly predicted ferroelectricity in CrI 3 via gating-induced Jahn–Teller distortion. Furthermore, our work illuminates the potential of 2D magnets in developing next-generation advanced computing technologies.

2D magnet↗

DOE OSTI2023

Controllable superconducting to semiconducting phase transition in topological superconductor 2M-WS 2

The investigation of exotic properties in two-dimensional (2D) topological superconductors has garnered increasing attention in condensed matter physics, particularly for applications in topological qubits. Despite this interest, a reliable way of fabricating topological Josephson junctions (JJs) utilizing topological superconductors has yet to be demonstrated. Controllable structural phase transition presents a unique approach to achieving topological JJs in atomically thin 2D topological superconductors. In this work, we report the pioneering demonstration of a structural phase transition from the superconducting to the semiconducting phase in the 2D topological superconductor 2M-WS 2 . We reveal that the metastable 2M phase of WS 2 remains stable in ambient conditions but transitions to the 2H phase when subjected to temperatures above 150°C. We further locally induced the 2H phase within 2M-WS 2 nanolayers using laser irradiation. Notably, the 2H phase region exhibits a hexagonal shape, and scanning tunneling microscopy (STM) uncovers an atomically sharp crystal structural transition between the 2H and 2M phase regions. Moreover, the 2M to 2H phase transition can be induced at the nanometer scale by a 200 keV electron beam. The electrical transport measurements further confirmed the superconductivity of the pristine 2M-WS 2 and the semiconducting behavior of the laser-irradiated 2M-WS 2 . Furthermore, our results establish a novel approach for controllable topological phase change in 2D topological superconductors, significantly impacting the development of atomically scaled planar topological JJs.

2D materials↗