arXiv subjects

Yingying Cao

Publications and source records attributed to Yingying Cao.

7 recordsLinked to original sources

arXiv2026

Pressure-induced self-doping and Fermi surface reconstruction in UAs2

Superconductivity has recently been reported in the heavy-fermion compound UAs2 under pressure, with the highest Tc among uranium-based correlated 5f-electron superconductors. To elucidate its microscopic origin, we investigate its electronic structure using density functional theory combined with dynamical mean-field theory (DFT+DMFT). At ambient pressure, our calculations reproduce the characteristic Kondo-lattice electronic structure, with flat hybridization bands near the Fermi energy around the {\Gamma} and M points, in good agreement with angle-resolved photoemission spectroscopy (ARPES). Under pressure, we find a systematic transfer of electrons from the more localized 5f5/2 orbitals to the more itinerant 5f7/2 orbitals, while the total U-5f occupancy remains nearly unchanged. This orbital-selective charge redistribution constitutes a pressure-induced self-doping effect that drives the 5f5/2 electrons from a localized Kondo regime toward a mixed-valence regime with enhanced charge fluctuations, leading to a dramatic reconstruction of the low-energy electronic structure. Remarkably, superconductivity emerges in the pressure range where the Fermi surface consists of two disconnected sheets with enhanced nesting, but disappears when they bend and merge into a corrugated three-dimensional cylinder. Our results provide an electronic-structure basis for understanding superconductivity in UAs2 and suggest that Fermi-surface nesting and charge fluctuations may contribute to the enhanced superconducting Tc, pointing to a possible distinction from conventional heavy-fermion superconductors.

cond-mat.str-el↗

arXiv2026

Correlated topological band structures of the kagome altermagnets Mn$_3X$ ($X=$ Sn, Ge, Ga)

The interplay of topological band structures and electronic correlations may lead to novel quantum phenomena with potential applications. First-principles calculations are critical for guiding experimental discoveries and interpretations, but often fail if electronic correlations cannot be properly treated. Here we show that this issue occurs also in the kagome altermagnets Mn$_3X$ ($X=$ Sn, Ge, Ga), which were believed to exhibit large anomalous Hall effect due to topological band structures with Weyl nodes near the Fermi energy. Our systematic investigations reveal critical importance of beyond-DFT treatments on three key aspects of their magnetic, electronic, and topological properties: (1) establishment of noncollinear altermagnetic orders, (2) weakly renormalized band structures in excellent agreement with angle-resolved photoemission spectroscopy experiment, and (3) sensitive tuning of the Weyl nodes. Our work provides a unified basis for understanding topological properties of the Mn$_3X$ family, which challenges previous experimental interpretations based on DFT band structures and predicts potentially higher anomalous Hall conductivity in Mn$_3$Ga under electron doping. This underscores the importance of a correlation-aware framework beyond DFT in understanding topological magnetic materials.

cond-mat.mtrl-sci↗

arXiv2025

Optimization of target film materials and protective coatings for sealed neutron generator

Magnesium target film has better thermal stability and neutron yield than titanium target, making it a potential neutron generator target film material. The radiation resistance of elemental magnesium targets is relatively weak, and their radiation resistance can be improved by alloying magnesium target films. The irradiation damage of pure magnesium targets and magnesium alloy target films was studied using SRIM. The results indicate that the irradiation damage of magnesium alloy target films (magnesium-niobium, magnesium-zirconium alloys) is lower than that of pure magnesium targets. In addition, under the same alloy ratio, the radiation resistance of magnesium-niobium alloy target film is better than that of magnesium-zirconium alloy. In order to further in-vestigate the performance of magnesium alloy target films, the incident ion energy, protective coatings (nickel oxide, aluminum oxide, palladium oxide), magnesium alloy target films, and alloy doping ratios (0.2, 0.4, 0.6, 0.8, 1.0) were changed. After calculating the effects of the above conditions on the neutron generator yield, sputtering yield, and considering irradiation damage, it was determined that a magnesium-zirconium alloy with a doping rate of 0.2 and a nickel oxide protective coating with a thickness of 7.5 nm are potential target film materials for the neutron generator.

physics.ins-det↗

arXiv2025

Weak electronic correlations in the cobalt oxychalcogenide superconductor Na2CoSe2O

Motivated by the newly discovered Co-based superconductor Na2CoSe2O, we performed systematic calculations of its electronic band structures using the density functional theory (DFT) plus the dynamical mean-field theory (DMFT) approaches. Our comparative studies reveal weakly correlated and itinerant nature of the Co-3d electrons and show no sign of fluctuating local moments as expected in many other unconventional superconductors, although the Co eg orbitals are close to half filling. These suggest that Na2CoSe2O is a normal paramagnetic metal and its superconductivity might not be of strongly correlated nature, contrary to the initial speculation. We suggest future investigations of electron-phonon interactions to clarify its pairing mechanism.

cond-mat.str-el↗

arXiv2023

A Weakly Supervised Segmentation Network Embedding Cross-scale Attention Guidance and Noise-sensitive Constraint for Detecting Tertiary Lymphoid Structures of Pancreatic Tumors

The presence of tertiary lymphoid structures (TLSs) on pancreatic pathological images is an important prognostic indicator of pancreatic tumors. Therefore, TLSs detection on pancreatic pathological images plays a crucial role in diagnosis and treatment for patients with pancreatic tumors. However, fully supervised detection algorithms based on deep learning usually require a large number of manual annotations, which is time-consuming and labor-intensive. In this paper, we aim to detect the TLSs in a manner of few-shot learning by proposing a weakly supervised segmentation network. We firstly obtain the lymphocyte density maps by combining a pretrained model for nuclei segmentation and a domain adversarial network for lymphocyte nuclei recognition. Then, we establish a cross-scale attention guidance mechanism by jointly learning the coarse-scale features from the original histopathology images and fine-scale features from our designed lymphocyte density attention. A noise-sensitive constraint is introduced by an embedding signed distance function loss in the training procedure to reduce tiny prediction errors. Experimental results on two collected datasets demonstrate that our proposed method significantly outperforms the state-of-the-art segmentation-based algorithms in terms of TLSs detection accuracy. Additionally, we apply our method to study the congruent relationship between the density of TLSs and peripancreatic vascular invasion and obtain some clinically statistical results.

eess.IV↗

arXiv2023

Flat bands promoted by Hund's rule coupling in the candidate double-layer high-temperature superconductor La$_3$Ni$_2$O$_7$

We report strongly correlated electronic band structure calculations of the recently discovered double-layer high-temperature superconductor La$_3$Ni$_2$O$_7$ under pressure. Our calculations reveal dual nature of Ni-$d$ electrons with almost localized $d_{z^2}$ orbitals due to onsite Coulomb repulsion and very flat hybridization bands of Ni-$d_{x^2-y^2}$ and Ni-$d_{z^2}$ quasiparticles near the Fermi energy. We find that the quasiparticle effective mass are greatly enhanced by the Hund's rule coupling and their lifetimes are inversely proportional to the temperature, which explains the experimentally observed strange metal behavior in the normal state. We also find strong antiferromagnetic spin correlations of Ni-$d$ electrons, which may provide the pairing force of quasiparticles for the high-temperature superconductivity. These give a potential explanation of two key observations in experiment and connect the superconducting La$_3$Ni$_2$O$_7$ with cuprate high-temperature superconductors. The presence of flat bands and the interplay of orbital-selective Mott, Hund, and Kondo physics make La$_3$Ni$_2$O$_7$ a unique platform for exploring rich emergent quantum many-body phenomena in the future.

cond-mat.supr-con↗

arXiv2020

Observation of flat bands due to band hybridization in 3d-electron heavy-fermion compound CaCu3Ru4O12

We report angle-resolved photoemission spectroscopy and first-principles numerical calculations for the band structure evolution of the 3d heavy-fermion compound CaCu3Ru4O12. Below 200 K, we observed an emergent hybridization gap between the Cu 3d electron-like band and the Ru 4d hole-like band and the resulting flat band features near the Fermi energy centered around the Brillouin zone corner. Our results confirm the non-Kondo nature of CaCu3Ru4O12, in which the Cu 3dxy electrons are less correlated and not in the Kondo limit. Comparison between theory and experiment also suggests that other mechanism such as nonlocal interactions or spin fluctuations beyond the local dynamical mean-field theory may be needed in order to give a quantitative explanation of the peculiar properties in this material.

cond-mat.str-el↗