arXiv subjects

Yapeng Wu

Publications and source records attributed to Yapeng Wu.

4 recordsLinked to original sources

arXiv2026

Charge-Density-Wave Phase Selection by Janus-Induced Intrinsic Strain in Monolayer NbSSiAs$_2$

Controlling phase selection among competing charge-density-wave (CDW) instabilities remains challenging in two-dimensional materials. Here, first-principles calculations show that Janus-induced intrinsic tensile strain redirects the off-M soft-mode tendency of NbS$_2$ to the M point in NbSSiAs$_2$, selecting a $2\times2$ CDW reconstruction. Electron-phonon coupling analysis identifies momentum-selective coupling between Nb-derived states and a longitudinal acoustic mode as the origin of the M-point instability. The reconstructed phase hosts two nearly degenerate Nb-trimerized configurations whose relative stability is tuned by biaxial strain. Both configurations retain phonon-mediated superconductivity on the 6-7 K scale, indicating the coexistence of CDW order and superconductivity. Compressive strain favors the 1+3-hollow configuration and induces a band-inverted, $Z_2$-nontrivial state while preserving superconductivity. Together, these results identify Janus-induced intrinsic strain as an internal structural route for CDW phase selection, whereas external strain provides access to a regime in which CDW order, topology, and superconductivity coexist.

cond-mat.mtrl-sci↗

arXiv2026

Enhanced superconductivity in atomically thin noble metals: From quantum confinement to interface-induced Lifshitz transition

Unlocking superconductivity in intrinsically non-superconducting noble metals (Au, Ag, Cu) represents a fundamental challenge in low-dimensional physics. While quantum confinement in the atomically thin limit is known to trigger emergent superconductivity, strategies to amplify this marginal effect to experimentally accessible temperatures remain a key open question. Using first-principles calculations, we establish a unified framework linking intrinsic confinement effects with interface engineering in noble metal films. We reveal that intrinsic superconductivity is element-specific: it is suppressed in Ag by a stiff phonon spectrum, but emerges in trilayer Cu ($T_{\rm C} \approx 0.78$ K) and pentalayer Au ($0.63$ K) driven by confinement-induced density-of-states (DOS) enhancement and phonon softening, respectively. In h-BN/Cu(111) heterostructures, $T_{\rm C}$ is critically dictated by the interfacial stacking configuration. We identify the thermodynamically stable N-bonded interface as a reliable platform for accessible superconductivity ($T_{\rm C} \approx 3.23$ K), whereas manipulating the system into a metastable B-bonded configuration boosts $T_{\rm C}$ to $7.00$ K. This enhancement originates from a B-bonded-induced Lifshitz transition, where the Fermi surface forms a tangential contact with the Brillouin zone boundary at the M point, enhancing electron-phonon coupling beyond DOS effects. Our work unifies the understanding of intrinsic two-dimensional superconductivity with atomistic interface design, offering a blueprint for functionalizing noble metals as emergent superconductors.

cond-mat.supr-con↗

arXiv2023

A Deep-learning Real-time Bias Correction Method for Significant Wave Height Forecasts in the Western North Pacific

Significant wave height is one of the most important parameters characterizing ocean waves, and accurate numerical ocean wave forecasting is crucial for coastal protection and shipping. However, due to the randomness and nonlinearity of the wind fields that generate ocean waves and the complex interaction between wave and wind fields, current forecasts of numerical ocean waves have biases. In this study, a spatiotemporal deep-learning method was employed to correct gridded SWH forecasts from the ECMWF-IFS. This method was built on the trajectory gated recurrent unit deep neural network,and it conducts real-time rolling correction for the 0-240h SWH forecasts from ECMWF-IFS. The correction model is co-driven by wave and wind fields, providing better results than those based on wave fields alone. A novel pixel-switch loss function was developed. The pixel-switch loss function can dynamically fine-tune the pre-trained correction model, focusing on pixels with large biases in SWH forecasts. According to the seasonal characteristics of SWH, four correction models were constructed separately, for spring, summer, autumn, and winter. The experimental results show that, compared with the original ECMWF SWH predictions, the correction was most effective in spring, when the mean absolute error decreased by 12.972~46.237%. Although winter had the worst performance, the mean absolute error decreased by 13.794~38.953%. The corrected results improved the original ECMWF SWH forecasts under both normal and extreme weather conditions, indicating that our SWH correction model is robust and generalizable.

physics.ao-ph↗

arXiv2022

New classes of permutation polynomials with coefficients 1 over finite fields

Permutation polynomials with coefficients 1 over finite fields attract researchers' interests due to their simple algebraic form. In this paper, we first construct four classes of fractional permutation polynomials over the cyclic subgroup of $ \mathbb{F}_{2^{2m}} $. From these permutation polynomials, three new classes of permutation polynomials with coefficients 1 over $ \mathbb{F}_{2^{2m}} $ are constructed, and three more general new classes of permutation polynomials with coefficients 1 over $ \mathbb{F}_{2^{2m}} $ are constructed using a new method we presented recently. Some known permutation polynomials are the special cases of our new permutation polynomials. Furthermore, we prove that, in all new permutation polynomials, there exists a permutation polynomial which is EA-inequivalent to known permutation polynomials for all even positive integer $ m $. This proof shows that EA-inequivalent permutation polynomials over $ \mathbb{F}_{q} $ can be constructed from EA-equivalent permutation polynomials over the cyclic subgroup of $ \mathbb{F}_{q} $. From this proof, it is obvious that, in all new permutation polynomials, there exists a permutation polynomial of which algebraic degree is the maximum algebraic degree of permutation polynomials over $ \mathbb{F}_{2^{2m}} $.

math.NT↗