arXiv subjects

Dehong Yang

Publications and source records attributed to Dehong Yang.

7 recordsLinked to original sources

arXiv2026

Profile decomposition, strict binding and global compactness for a critical Grushin embedding

We study attainment of the best constant in \begin{equation*} \int_{\mathbb R^{m+n}} \bigl(|\nabla_xu|^2+|x|^2|\nabla_yu|^2+a|u|^2\bigr) \geq S_a\left(\int_{\mathbb R^{m+n}} (1+|x|^2)^{n/(Q-2)}|u|^q\right)^{2/q}, \end{equation*} where $m,n\geq1$, $Q=m+2n$, $q=2Q/(Q-2)$, and $a>0$. Using annular interpolation and a transverse-average recurrence with $L^q$ contraction $2^{-m/q}$, we decompose bounded sequences into finite, Grushin and Euclidean profiles. Energy and critical mass split, with a power bound in the number of profiles on the remaining mass. We prove compactness of normalized minimizing sequences modulo $y$-translations under $S_a<\min\{S_G,a^{n/Q}S_E(1)\}$, where $S_G$ and $S_E(1)$ are the tangent constants. The strict-binding set is empty or an open interval; we prove nonemptiness for $n=1$ and even $m\geq6$. At finite positive endpoints of a nonempty binding interval, we characterize attainment by first-order binding gaps. We obtain a finite critical-profile decomposition of Palais--Smale sequences with a remainder vanishing in energy.

math.AP↗

arXiv2026

Sharp fractional Hardy--Maz'ya remainders on half-spaces: angular reduction and energy stability

For $d\geq2$, $0 1$, and $τ>0$, we study the sharp half-space remainder \[ [u]_{s,p,+}^p-\mathcal D_{d,s,p}\int_{\mathbb R^d_+}x_d^{-sp}|u|^p\,dx \geqΛ_{d,s,p,τ}\int_{\mathbb R^d_+} \frac{x_d^{τ-sp}|u|^p}{(x_{d-1}^2+x_d^2)^{τ/2}}\,dx. \] We first obtain exact dimensional and angular reductions by an $L^p$ contraction. For $p=2$, we identify the planar sharp coefficient with the simple first eigenvalue of a singular angular operator with compact resolvent. We prove a ground-state representation and a two-sided estimate for the sharp deficit. These give quantitative stability and a Fourier--Mellin energy criterion for extremizing sequences in all dimensions. For the distance with multiplier $h(ξ)=\min\{ξ^2,1\}$, the best planar stability coefficient is not attained and is strictly smaller than the quadratic dispersion coefficient. The minimizing frequencies are nonzero when $τ=2$ and $s$ is close to one. Finally, we prove normalized local limits for the sharp quadratic constant, each fixed fiber eigenvalue, and the dispersion coefficient.

math.AP↗

arXiv2026

Ultrafast Non-Volatile Weyl LuminoMem for Mid-Infrared In-Memory Computing

Integrated optoelectronic systems strive to combine the logic/memory density of electronics with the bandwidth of photonics, but monolithic realization is impeded by the inefficient electronic-to-photonic interface. Current architectures rely on separate readout circuitry and modulators, creating bottlenecks in energy and latency, while existing direct transduction methods often compromise on switching speed or non-volatility. Here, we report an ultrafast, non-volatile optoelectronic memory, named LuminoMem, that integrates electrical storage and mid-infrared light emission in a single device. The device utilizes a floating-gate architecture, in which the Weyl semiconductor tellurium serves simultaneously as a charge-trapping storage layer and an emissive medium. This design enables nanosecond-scale electrical programming of non-volatile photoluminescence at 3.4 um, allowing direct optical access to stored states without external modulation. We demonstrate 4-bit (16-level) optical storage capacity and validate the device's performance through neural network simulations that achieve high accuracy on the Fashion-MNIST dataset. By effectively bridging the gap between electronic storage and mid-infrared photonics, the demonstrated mid-infrared LuminoMem provides a hardware foundation for promoting current computation efficiency and potential intelligent platforms that co-integrate computing, memory, and sensing capabilities.

cond-mat.mtrl-sci↗

arXiv2026

Direct Photocurrent Detection of Optical Vortex Based on the Orbital Photo Galvanic Effect: Progress, Challenge and Perspective

A photodetector that can directly distinguish the orbital angular momentum (OAM) of light is highly desirable for integrated on-chip OAM detection and focal plane array devices. The recent development of OAM detectors based on the intrinsic orbital photo galvanic effects (OPGE) of materials provide a new route for direct OAM detection that is on-chip scalable with high resolution and speed. In this paper, we summarize the current progress in direct photodetection of OAM via OPGE. We begin with a short review of the basic operation scheme of the OAM detector and provide a comprehensive symmetry analysis to sort out the favorable characteristics of the materials, incorporating considerations from device schemes based on various device performance characteristics and specific application circumstances. From that, we review the current experimental progress and technical challenges, then oversee the possible solutions to these challenges and provide a perspective on the future opportunities of this OAM detection route.

cond-mat.mtrl-sci↗

arXiv2025

Versatile tunable optical injection of chiral polarized Weyl fermions in a magnetic Weyl semimetal Co3Sn2S2

Precise probe and control of various quantum degrees of freedom in novel quantum matter are central to understanding fundamental quantum physics and hold promise for innovative routes to encode and process information. Chirality is one such degree of freedom that has recently attracted intense research interest, especially for Weyl fermions in topological Weyl semimetals. The coupling of chiral degrees of freedom through light-matter interactions and the versatile control of these couplings through external fields can lead to precise quantum control of Weyl fermions. In this work, we demonstrate the observation of light chirality-dependent photocurrent in the mid-infrared regime. Excitation wavelength-dependent measurements reveal that the photocurrent originates from the injection of chiral polarized Weyl fermions by chiral polarized mid-infrared photons. The optical process that generates unbalanced chiral polarized Weyl fermions is determined to be a third-order nonlinear photocurrent process. Compared with nonmagnetic Weyl semimetals, such coupling is versatilely tunable in magnetic Weyl semimetals with the magnetization direction and external electric field in addition to the chirality of light. Our results are not only directly applicable to tunable circular-polarization-sensitive photodetection in the mid-infrared regime, but also pave the way toward functional quantum devices that utilize the chiral quantum degrees of freedom of Weyl fermions.

cond-mat.mes-hall↗

arXiv2025

Observation of Berry Curvature-Enhanced Anomalous Photo-Nernst Effect in Magnetic Weyl Semimetal

The anomalous Nernst effect is the thermoelectric counterpart of the anomalous Hall effect, which can emerge in magnetic materials or topological materials without magnetic field. Such effect is critical to both fundamental topological physics and various application fields, including energy harvesting, spintronics and optoelectronics. In this work, we observe the anomalous photo-Nernst effect, which use light excitation to generate temperature gradients for the thermoelectric response. Our experiments reveal a pronounced edge photocurrent response in magnetic Weyl semimetal Co3Sn2S2 under zero magnetic field, originating from the anomalous photo-Nernst effect. The pronounced photo-Nernst current benefits from the exceptional properties of Co3Sn2S2, including the large thermoelectric coefficient, topologically enhanced anomalous response of Weyl bands and the Shockley-Ramo nature of long-range photocurrent generation. Furthermore, by comparing the nominal anomalous Nernst coefficient under different wavelength excitations, we observe a clear enhancement in the mid-infrared region, originating from the topological contribution from the large Berry curvature of Weyl bands. Our results reveal the interplay among light, magnetism, and topological order in magnetic Weyl semimetals, which not only offers insights for fundamental physics but also advances potential applications in quantum devices.

cond-mat.mtrl-sci↗

arXiv2025

High-speed readout for direct light orbital angular momentum photodetector via photoelastic modulation

Recent progress in direct photodetection of light orbital angular momentum (OAM) based on the orbital photogalvanic effect (OPGE) provides an effective way for on-chip direct electric readout of orbital angular momentum, as well as large-scale integration focal-plane array devices. However, the recognition of OAM order from photocurrent response requires the extraction of circular polarization-dependent response. To date, the operation speed of such detector is currently at the minute level and is limited by slow mechanical polarization modulation and low OAM recognition capability. In this work, we demonstrate that the operation speed can be greatly improved via electrical polarization modulation strategy with photoelasitc modulator accompanied by phase-locked readout approach with lock-in amplifier. We demonstrate an operation speed of up to 1 kHz with this new technology in the mid-infrared region (4 μm) on an OAM detector using multilayer graphene (MLG) as photosensitive material. In principle, with new modulation and readout scheme, we can potentially increase the operation speed to 50.14 kHz with a PEM that operates at a state-of-the-art speed. Our work paves the way toward high-speed operation of direct OAM detection devices based on OPGE effect and pushes such technology to a more practical stage for focal plane array applications.

physics.optics↗