arXiv subjects

Yongfeng Lu

Publications and source records attributed to Yongfeng Lu.

3 recordsLinked to original sources

arXiv2026

Interface Control of Second-Harmonic Generation in Layered CuInP2S6 via PbZr0.2Ti0.8O3 Domain Wall

The control of nonlinear optical responses in van der Waals ferroelectrics at the nanoscale offers opportunities for developing two-dimensional integrated nanophotonics with programmable functionalities. In this work, we report the first realization of nanoscale nonvolatile control of the amplitude and polarization of second-harmonic generation (SHG) response in layered CuInP2S6 (CIPS) via the domain structure in an interfacial PbZr0.2Ti0.8O3 (PZT) thin film. The SHG intensity at CIPS/PZT heterointerface is continuously modulated, either substantially enhanced or almost entirely quenched, by the circular domain walls in underlying ferroelectric oxide. The interfacial coupling of CIPS polar axis with in-plane polarization of PZT domain walls tailors the SHG light polarization into two-fold (C2V) symmetry, which is well modeled by nonlinear electromagnetic theory. Overall, this study enables nonvolatile programmable design of nonlinear light intensity and polarization in van der Waals ferroelectrics at the nanoscale.

cond-mat.mtrl-sci↗

arXiv2025

Engineering Phonons in Compositionally Complex Carbide Ceramics

In the pursuit of advanced ceramic materials with exceptional irradiation-resistance and high-temperature tolerance for nuclear applications, compositionally complex carbides (CCCs) have emerged as a highly promising class of candidate materials for extreme environments. In such conditions, critical material properties such as thermal stability, elasticity, thermal conductivity and thermodynamics behavior are predominantly influenced by phonons. In CCCs, pronounced cation disorder can lead to significant phonon scattering due to inherent mass and force constant variations, impacting these critical properties. In this study, we used ab initio calculations to predict the phonon band structures and systematically explore the influence of mass and force constant variance on the phonon spectral function of CCCs with a rock salt structure, ranging from binary to five-metal component carbides. Our findings reveal that the selection and concentration of constituent elements can be strategically utilized to tune the phonon band structure, phonon bandgap and phonon scattering in CCCs, thereby enabling control over phonon-related properties. Additionally, we measured the thermal conductivity of some of these CCCs using the spatial-domain thermoreflectance technique. Interestingly, the measured thermal conductivity of some of these CCCs indicates that five-component ceramics exhibit higher thermal conductivity than certain ternary and binary alloys. This observation contrasts with the expectation that greater cation disorder would result in more scattering and lower thermal conductivity. This intriguing result opens up the possibility of discovering CCCs with better thermal conductivity, presenting new opportunities for their application in extreme environments.

cond-mat.mtrl-sci↗

arXiv2020

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.

cond-mat.mes-hall↗