Nodeless Superconductivity in Kagome Metal CsV3Sb5 with and without Time Reversal Symmetry Breaking.

The kagome metal CsV3Sb5 features an unusual competition between the charge-density-wave (CDW) order and superconductivity. Evidence for time reversal symmetry breaking (TRSB) inside the CDW phase has been accumulating. Hence, the superconductivity in CsV3Sb5 emerges from a TRSB normal state, potentially resulting in an exotic superconducting state. To reveal the pairing symmetry, we first investigate the effect of nonmagnetic impurity. Our results show that the superconducting critical temperature is insensitive to disorder, pointing to conventional s-wave superconductivity. Moreover, our measurements of the self-field critical current (Ic,sf), which is related to the London penetration depth, also confirm conventional s-wave superconductivity with strong coupling. Finally, we measure Ic,sf where the CDW order is removed by pressure and superconductivity emerges from the pristine normal state. Our results show that s-wave gap symmetry is retained, providing strong evidence for the presence of conventional s-wave superconductivity in CsV3Sb5 irrespective of the presence of the TRSB.

Fragile Pressure-Induced Magnetism in FeSe Superconductors with a Thickness Reduction.

The emergence of high transition temperature (Tc) superconductivity in bulk FeSe under pressure is associated with the tuning of nematicity and magnetism. However, sorting out the relative contributions from magnetic and nematic fluctuations to the enhancement of Tc remains challenging. Here, we design and conduct a series of high-pressure experiments on FeSe thin flakes. We find that as the thickness decreases the nematic phase boundary on temperature-pressure phase diagrams remains robust while the magnetic order is significantly weakened. A local maximum of Tc is observed outside the nematic phase region, not far from the extrapolated nematic end point in all samples. However, the maximum Tc value is reduced associated with the weakening of magnetism. No high-Tc phase is observed in the thinnest sample. Our results strongly suggest that nematic fluctuations alone can only have a limited effect while magnetic fluctuations are pivotal on the enhancement of Tc in FeSe.

TO-UGDA: target-oriented unsupervised graph domain adaptation.

Graph domain adaptation (GDA) aims to address the challenge of limited label data in the target graph domain. Existing methods such as UDAGCN, GRADE, DEAL, and COCO for different-level (node-level, graph-level) adaptation tasks exhibit variations in domain feature extraction, and most of them solely rely on representation alignment to transfer label information from a labeled source domain to an unlabeled target domain. However, this approach can be influenced by irrelevant information and usually ignores the conditional shift of the downstream predictor. To effectively address this issue, we introduce a target-oriented unsupervised graph domain adaptive framework for graph adaptation called TO-UGDA. Particularly, domain-invariant feature representations are extracted using graph information bottleneck. The discrepancy between two domains is minimized using an adversarial alignment strategy to obtain a unified feature distribution. Additionally, the meta pseudo-label is introduced to enhance downstream adaptation and improve the model's generalizability. Through extensive experimentation on real-world graph datasets, it is proved that the proposed framework achieves excellent performance across various node-level and graph-level adaptation tasks.

Activation and tolerance of Siegesbeckia Orientalis L. rhizosphere to Cd stress.

This experiment investigated the changes of rhizosphere soil microenvironment for hyperaccumulation-soil system under Cd stress in order to reveal the mechanism of hyperaccumulation and tolerance. Thus, Cd fractions, chemical compositions, and biochemical characteristics in rhizosphere soil of Siegesbeckia orientalis L. under Cd stress conditions of 0, 5, 10, 25, 50, 100, and 150 mg kg-1 were investigated through a root bag experiment, respectively. As a result, Cd induced the acidification of S. orientalis rhizosphere soil, and promoted the accumulation of dissolved organic carbon (DOC) and readily oxidizable organic carbon (ROC), which increased by 28.39% and 6.98% at the maximum compared with control. The percentage of labile Cd (acid-soluble and reducible Cd) in soil solution increased significantly (P < 0.05) from 31.87% to 64.60% and from 26.00% to 34.49%, respectively. In addition, rhizosphere microenvironment can alleviate the inhibition of Cd on soil microorganisms and enzymes compare with bulk soils. Under medium and low concentrations of Cd, the rhizosphere soil microbial biomass carbon (MBC), basal respiration, ammonification and nitrification were significantly increased (P < 0.05), and the activities of key enzymes were not significantly inhibited. This suggests that pH reduction and organic carbon (DOC and ROC) accumulation increase the bioavailability of Cd and may have contributed to Cd accumulation in S. orientalis. Moreover, microorganisms and enzymes in rhizosphere soils can enhance S. orientalis tolerance to Cd, alleviating the nutrient imbalance and toxicity caused by Cd pollution. This study revealed the changes of physicochemical and biochemical properties of rhizosphere soil under Cd stress. Rhizosphere soil acidification and organic carbon accumulation are key factors promoting Cd activation, and microorganisms and enzymes are the responses of Cd tolerance.

Polar Nitride Perovskite LaWN3-δ with Orthorhombic Structure.

Nitride perovskite LaWN3 has been predicted to be a promising ferroelectric material with unique properties for diverse applications. However, due to the challenging sample preparation at ambient pressure, the crystal structure of this nitride remains unsolved, which results in many ambiguities in its properties. Here, the authors report a comprehensive study of LaWN3 based on high-quality samples synthesized by a high-pressure method, leading to a definitive resolution of its crystal structure involving nitrogen deficiency. Combined with theoretical calculations, these results show that LaWN3 adopts an orthorhombic Pna21 structure with a polar symmetry, possessing a unique atomic polarization along the c-axis. The associated atomic polar distortions in LaWN3 are driven by covalent hybridization of W: 5d and N: 2p orbitals, opening a direct bandgap that explains its semiconducting behaviors. The structural stability and electronic properties of this nitride are also revealed to be closely associated with its nitrogen deficiency. The success in unraveling the structural and electronic ambiguities of LaWN3 would provide important insights into the structures and properties of the family of nitride perovskites.

Patterned diamond anvils prepared via laser writing for electrical transport measurements of thin quantum materials under pressure.

Quantum materials exhibit intriguing properties with important scientific values and huge technological potential. Electrical transport measurements under hydrostatic pressure have been influential in unraveling the underlying physics of many quantum materials in bulk form. However, such measurements have not been applied widely to samples in the form of thin flakes, in which new phenomena can emerge, due to the difficulty in attaching fine wires to a thin sample suitable for high-pressure devices. Here, we utilize a home-built direct laser writing system to functionalize a diamond anvil to directly integrate the capability of conducting electrical transport measurements of thin flakes with a pressure cell. With our methodology, the culet of a diamond anvil is equipped with a set of custom-designed conducting tracks. We demonstrate the superiority of these tracks as electrodes for the studies of thin flakes by presenting the measurement of pressure-enhanced superconductivity and quantum oscillations in a flake of MoTe2.