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Shao, Ding-Fu

Publications and source records attributed to Shao, Ding-Fu.

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Tilted spin current generated by the collinear antiferromagnet ruthenium dioxide

Symmetry plays a central role in determining the polarization of spin currents induced by electric fields. It also influences how these spin currents generate spin-transfer torques in magnetic devices. Here, we show that an out-of-plane damping-like torque can be generated in ruthenium oxide (RuO 2 )/permalloy devices when the Néel vector of the collinear antiferromagnet RuO 2 is canted relative to the sample plane. By measuring characteristic changes in all three components of the electric-field-induced torque vector as a function of the angle of the electric field relative to the crystal axes, we find that the RuO 2 generates a spin current with a well-defined tilted spin orientation that is approximately parallel to the Néel vector. A maximum out-of-plane damping-like spin torque efficiency per unit electric field of 7±1 × 10 3 Ω -1 m -1 is measured at room temperature. Here, the observed angular dependence indicates that this is an antiferromagnetic spin Hall effect with symmetries that are distinct from other mechanisms of spin-current generation reported in antiferromagnetic and ferromagnetic materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Giant Transport Anisotropy in ReS 2 Revealed via Nanoscale Conducting-Path Control

The low in-plane symmetry in layered 1T'-ReS 2 results in strong band anisotropy, while its manifestation in the electronic properties is challenging to resolve due to the lack of effective approaches for controlling the local current path. In this work, we reveal the giant transport anisotropy in monolayer to four-layer ReS 2 by creating directional conducting paths via nanoscale ferroelectric control. By reversing the polarization of a ferroelectric polymer top layer, we induce conductivity switching ratio of >1.5×10 8 in the ReS 2 channel at 300 K. Characterizing the domain-defined conducting nanowires in an insulating background shows that the conductivity ratio between the directions along and perpendicular to the Re-chain can exceed 5.5×10 4 in monolayer ReS 2 . Theoretical modeling points to the band origin of the transport anomaly, and further reveals the emergence of a flat band in few-layer ReS 2 . Our work paves the path for implementing the highly anisotropic 2D materials for designing novel collective phenomena and electron lensing applications.

2D van der Waals materials↗
DOE OSTI2020

Polar coupling enabled nonlinear optical filtering at MoS 2 /ferroelectric heterointerfaces

Complex oxide heterointerfaces and van der Waals heterostructures present two versatile but intrinsically different platforms for exploring emergent quantum phenomena and designing new functionalities. The rich opportunity offered by the synergy between these two classes of materials, however, is yet to be charted. Here, we report an unconventional nonlinear optical filtering effect resulting from the interfacial polar alignment between monolayer MoS 2 and a neighboring ferroelectric oxide thin film. The second harmonic generation response at the heterointerface is either substantially enhanced or almost entirely quenched by an underlying ferroelectric domain wall depending on its chirality, and can be further tailored by the polar domains. Unlike the extensively studied coupling mechanisms driven by charge, spin, and lattice, the interfacial tailoring effect is solely mediated by the polar symmetry, as well explained via our density functional theory calculations, pointing to a new material strategy for the functional design of nanoscale reconfigurable optical applications.

36 MATERIALS SCIENCE↗