arXiv subjects

Pengyu Zheng

Publications and source records attributed to Pengyu Zheng.

12 recordsLinked to original sources

arXiv2026

Prediction of BaBiO$_3$-like superconducting perovskites in K-doped SrAsO$_3$

Using first-principles calculations, we predict a new perovskite compound SrAsO$_3$ . The undoped cubic phase has pronounced soft-phonon instabilities, which are gradually suppressed upon K doping the Sr site. The cubic phase becomes dynamically stable for K-doping levels above approximately 60%, and the stabilized K-doped phases are metallic with predicted conventional phonon mediated superconductivity. Moreover, the inclusion of nonlocal exchange interactions broadens the electronic bandwidth, enhances the electron-phonon coupling (EPC) strength, and increases the superconducting transition temperature ($T_c$) of these doped compounds. In particular, the HSE06 hybrid exchange-correlation functional corrected EPC constant $λ$ reaches 1.41 for Sr$_{0.4}$K$_{0.6}$AsO$_3$, corresponding to a predicted $T_c$ of 44.3 K. These results suggest that SrAsO$_3$ is a BaBiO$_3$-like superconducting perovskite driven by strong electron-phonon coupling.

cond-mat.supr-con↗

arXiv2026

Enhanced Anomalous Nernst Effect in the Ferromagnetic Kondo Lattice CeCo2As2

The anomalous Nernst effect (ANE), generating a voltage perpendicular to a temperature gradient due to magnetization, is closely linked to the Berry curvature (BC) near the Fermi energy in topological magnets. We report an enhanced spontaneous ANE in the ferromagnetic Kondo lattice CeCo2As2, which features Kondo-screened cerium-based 4f moments embedded in a ferromagnetic d-electron framework. The observed large anomalous Nernst coefficient, greater than the Seebeck coefficient, is attributed to the strong BC present in the f-orbital-dominated flat bands. The enhanced ANE in CeCo2As2 serves as a signature of the Fermi energy pinning within the topological flat band, highlighting the correlation-driven topology in the Kondo lattice.

cond-mat.str-el↗

arXiv2026

The giant anomalous Hall and Nernst effects in Kagome permanent magnets RCo5

Kagome lattice materials have attracted considerable attention due to their intriguing topological properties and potential applications in next-generation quantum and spintronic technologies. In particular, rare-earth permanent magnets with Kagome structure provide an ideal platform that combines robust magnetism with nontrivial quantum phenomena. However, their anomalous transport properties, particularly thermoelectric responses, remain insufficiently explored. In this work, we perform systematic first-principles calculations on the anomalous Hall and anomalous Nernst effects in Kagome permanent magnets RCo5 (R = Ce, La, Sm, Gd). We find that CeCo5 exhibits a pronounced anomalous Hall conductivity of about 1500 Omega^-1 cm^-1 while GdCo5 displays a substantial anomalous Nernst conductivity of 11 A m^-1 K^-1 within +/- 0.1 eV of the Fermi energy, both comparable to or surpassing the measured intrinsic values reported in many typical Weyl and Heusler magnets. These exceptional anomalous transport properties originate from Berry curvature hotspots near spin-orbit coupling induced band gaps. If validated, these theoretical predictions would be important for Berry-curvature-driven transport in magnetic intermetallics. Our results establish RCo5 compounds as versatile platforms for exploring Berry curvature-driven transport in tunable magnetic topological materials.

cond-mat.mtrl-sci↗

arXiv2025

Correlation tuned Fermi-arc topology in a Weyl ferromagnet

Electrons on Fermi arcs (FAs), a hallmark of Weyl semimetals, exhibit chiral transport harboring chiral anomaly, negative magnetoresistance, and Majorana zero modes. While FAs were observed in exemplary Weyl semimetal TaAs and Co3Sn2S2, the manipulation of FAs has been rarely explored. Here we take Co3Sn2S2 as an example and demonstrate that tuning the electronic correlation strength is an effective way to control the topology and connectivity of FAs. After achieving a good agreement with experimentally measured band structure by employing combined density functional theory and dynamical mean field theory (DFT+DMFT) calculations, we show that the experimental charge dynamics are well reproduced by DFT+DMFT calculations but not DFT calculations. Electronic correlation renormalizes the bands around the Fermi level and modifies the energy and location of Weyl points, and the resulting FAs. In particular, on the Co-terminated surface, the FAs are formed by connecting Weyl points located in adjacent Brillouin zones in DFT+DMFT calculations and experiments, in strong contrast to the FAs connecting Weyl points within the same Brillouin zone in DFT calculations. We further show the evolution of FAs with correlation and reveal a topological change of the FAs on the Sn-terminated surface at stronger correlation strength. Our study sheds new light on experimental manipulation of FAs to improve the electronic properties of correlated Weyl semimetals.

cond-mat.mtrl-sci↗

arXiv2024

A topological Hund nodal line antiferromagnet

The interplay of topology, magnetism, and correlations gives rise to intriguing phases of matter. In this study, through state-of-the-art angle-resolved photoemission spectroscopy, density functional theory and dynamical mean-field theory calculations, we visualize a fourfold degenerate Dirac nodal line at the boundary of the bulk Brillouin zone in the antiferromagnet YMn2Ge2. We further demonstrate that this gapless, antiferromagnetic Dirac nodal line is enforced by the combination of magnetism, space-time inversion symmetry and nonsymmorphic lattice symmetry. The corresponding drumhead surface states traverse the whole surface Brillouin zone. YMn2Ge2 thus serves as a platform to exhibit the interplay of multiple degenerate nodal physics and antiferromagnetism. Interestingly, the magnetic nodal line displays a d-orbital dependent renormalization along its trajectory in momentum space, thereby manifesting Hund coupling. Our findings offer insights into the effect of electronic correlations on magnetic Dirac nodal lines, leading to an antiferromagnetic Hund nodal line.

cond-mat.str-el↗

arXiv2024

A Unified Framework for Microscopy Defocus Deblur with Multi-Pyramid Transformer and Contrastive Learning

Defocus blur is a persistent problem in microscope imaging that poses harm to pathology interpretation and medical intervention in cell microscopy and microscope surgery. To address this problem, a unified framework including the multi-pyramid transformer (MPT) and extended frequency contrastive regularization (EFCR) is proposed to tackle two outstanding challenges in microscopy deblur: longer attention span and data deficiency. The MPT employs an explicit pyramid structure at each network stage that integrates the cross-scale window attention (CSWA), the intra-scale channel attention (ISCA), and the feature-enhancing feed-forward network (FEFN) to capture long-range cross-scale spatial interaction and global channel context. The EFCR addresses the data deficiency problem by exploring latent deblur signals from different frequency bands. It also enables deblur knowledge transfer to learn cross-domain information from extra data, improving deblur performance for labeled and unlabeled data. Extensive experiments and downstream task validation show the framework achieves state-of-the-art performance across multiple datasets. Project page: https://github.com/PieceZhang/MPT-CataBlur.

cs.CV↗

arXiv2023

Observation of Kondo lattice and Kondo-enhanced anomalous Hall effect in an itinerant ferromagnet

The interplay between Kondo screening and magnetic interactions is central to comprehending the intricate phases in heavy-fermion compounds. However, the role of the itinerant magnetic order, which is driven by the conducting (c) electrons, has been largely uncharted in the context of heavy-fermion systems due to the scarcity of material candidates. Here we demonstrate the coexistence of the coherent Kondo screening and d-orbital ferromagnetism in material system La$_{1-x}$Ce$_x$Co$_2$As$_2$, through comprehensive thermodynamic and electrical transport measurements. Additionally, using angle-resolved photoemission spectroscopy (ARPES), we further observe the f-orbit-dominated bands near the Fermi level ($E_f$) and signatures of the f-c hybridization below the magnetic transition temperature, providing strong evidence of Kondo lattice state in the presence of ferromagnetic order. Remarkably, by changing the ratio of Ce/La, we observe a substantial enhancement of the anomalous Hall effect (AHE) in the Kondo lattice regime. The value of the Hall conductivity quantitatively matches with the first-principle calculation that optimized with our ARPES results and can be attributed to the large Berry curvature (BC) density engendered by the topological nodal rings composed of the Ce-4f and Co-3d orbitals at $E_f$. Our findings point to the realization of a new platform for exploring correlation-driven topological responses in a novel Kondo lattice environment.

cond-mat.str-el↗

arXiv2022

Correlation-corrected band topology and topological surface states in iron-based superconductors

Iron-based superconductors offer an ideal platform for studying topological superconductivity and Majorana fermions. In this paper, we carry out a comprehensive study of the band topology and topological surface states of a number of iron-based superconductors using a combination of density functional theory (DFT) and dynamical mean field theory. We find that the strong electronic correlation of Fe 3d electrons plays a crucial role in determining the band topology and topological surface states of iron-based superconductors. Electronic correlation not only strongly renormalizes the bandwidth of Fe 3d electrons, but also shifts the band positions of both Fe 3d and As/Se p electrons. As a result, electronic correlation moves the DFT-calculated topological surface states of many iron-based superconductors much closer to the Fermi level, which is crucial for realizing topological superconducting surface states and observing Majorana zero modes as well as achieving practical applications, such as quantum computation. More importantly, electronic correlation can change the band topology and make some iron-based superconductors topologically nontrivial with topological surface states whereas they have trivial band topology and no topological surface states in DFT calculations. Our paper demonstrates that it is important to take into account electronic correlation effects in order to accurately determine the band topology and topological surface states of iron-based superconductors and other strongly correlated materials.

cond-mat.supr-con↗

arXiv2022

Electronic structure and magnetism of the Hund insulator CrI3

CrI3 is a two-dimensional ferromagnetic van der Waals material with a charge gap of 1.1-1.2 eV. In this study, the electronic structure and magnetism of CrI3 are investigated by using density functional theory and dynamical mean-field theory. Our calculations successfully reproduce a charge gap of 1.1 eV in the paramagnetic state when a Hund coupling JH = 0.7 eV is included with an on-site Hubbard U = 5 eV. In contrast, with a large U value of 8 eV and negligible Hund coupling JH, CrI3 is predicted to be a moderately correlated metal in the paramagnetic state. We conclude that CrI3 is a Mott-Hund insulator due to the half-filled configuration of the Cr 3d t2g orbitals. The Cr 3d eg orbitals are occupied by approximately one electron, which leads to strong valence fluctuations so that the Cr 3d orbitals cannot be described by a single state. Moreover, at finite temperature, the calculated ordered static magnetic moment in the ferromagnetic state is significantly larger in the R3 phase than in the C2/m phase. This observation indicates that the structural phase transition from the C2/m phase to the R3 phase with decreasing temperature is driven by ferromagnetic spin fluctuations.

cond-mat.str-el↗

arXiv2022

Correlation-enhanced electron-phonon coupling and superconductivity in (Ba,K)SbO$_3$ superconductors

The electronic structure, lattice dynamics, and electron-phonon coupling (EPC) of the newly discovered (Ba,K)SbO$_3$ superconductors are investigated by first-principles calculations. The EPC of (Ba,K)SbO$_3$ is significantly enhanced by considering non-local electronic correlation using the Heyd-Scuseria-Ernzerhof hybrid exchange-correlation functional (HSE06). The EPC strength λ of Ba$_{0.35}$K$_{0.65}$SbO$_3$ is strongly increased from 0.33 in local-density approximation calculations to 0.59 in HSE06 calculations, resulting in a superconducting transition temperature Tc of about 14.9 K, which is in excellent agreement with experimental value of ~ 15 K. Our findings suggest (Ba,K)SbO$_3$ are extraordinary conventional superconductors, where non-local electronic correlation expands the bandwidth, enhances the EPC, and boosts the Tc. Moreover, we find both λ and Tc depend crucially on the K-doping level for (Ba,K)SbO$_3$ and (Ba,K)SbO$_3$ compounds. (Ba,K)SbO$_3$ have stronger EPC strength and higher Tc than those of (Ba,K)SbO$_3$ at the same K-doping level.

cond-mat.supr-con↗

arXiv2022

Ta2NiSe5: a candidate topological excitonic insulator with multiple band inversions

The electronic structures and topological properties of the orthorhombic and monoclinic phases of the quasi-one-dimensional excitonic insulator Ta2NiSe5 are investigated based on density functional theory. In contrast to a single parity or band inversion across the Fermi level in many topological insulators studied previously, there are multiple parity and band inversions with or without spin-orbit coupling in both phases of Ta2NiSe5, resulting in more complex and topologically nontrivial electronic structures. The Dirac cone type surface states of the low-temperature monoclinic phase are also obtained. In this paper, we demonstrate that Ta2NiSe5 is a promising candidate as a three-dimensional topological excitonic insulator.

cond-mat.mtrl-sci↗

arXiv2021

Computational design of a new layered superconductor LaOTlF2

A new layered compound LaOTlF2 is designed and investigated using first-principles calculations in this work. The parent compound is an insulator with an indirect band gap of 2.65 eV. Electron-doping of the parent compound makes the material metallic. In the meantime, several lattice vibrational modes couple strongly to the conduction band, leading to a large electron-phonon coupling constant and conventional superconductivity. The highest superconducting transition temperature Tc is predicted to be approximately 8.6 K with λ about 1.25 in the optimally doped LaO0.95F0.05TlF2, where λ is calculated using the Wannier interpolation technique.

cond-mat.supr-con↗