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"Hu, Wen"
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Twofold symmetry of c-axis resistivity in topological kagome superconductor CsV3Sb5 with in-plane rotating magnetic field
In transition metal compounds, due to the interplay of charge, spin, lattice and orbital degrees of freedom, many intertwined orders exist with close energies. One of the commonly observed states is the so-called nematic electron state, which breaks the in-plane rotational symmetry. This nematic state appears in cuprates, iron-based superconductor, etc. Nematicity may coexist, affect, cooperate or compete with other orders. Here we show the anisotropic in-plane electronic state and superconductivity in a recently discovered kagome metal CsV
3
Sb
5
by measuring
c
-axis resistivity with the in-plane rotation of magnetic field. We observe a twofold symmetry of superconductivity in the superconducting state and a unique in-plane nematic electronic state in normal state when rotating the in-plane magnetic field. Interestingly these two orders are orthogonal to each other in terms of the field direction of the minimum resistivity. Our results shed new light in understanding non-trivial physical properties of CsV
3
Sb
5
.
The recently discovered class of kagome metals AV
3
Sb
5
, where A stands for K, Rb, Cs, has been shown to host a variety of exotic phases. Here, the authors report the two-fold rotational symmetry of superconductivity and signatures of an in-plane nematic electronic state in CsV
3
Sb
5
under in-plane magnetic field.
Journal Article
Single particle tunneling spectrum of superconducting Nd1-xSrxNiO2 thin films
The pairing mechanism in cuprates remains as one of the most challenging issues in condensed matter physics. Recently, superconductivity was discovered in thin films of the infinite-layer nickelate Nd
1-x
Sr
x
NiO
2
(x = 0.12–0.25) which is believed to have the similar
3d
9
orbital electrons as that in cuprates. Here we report single-particle tunneling measurements on the superconducting nickelate thin films. We find predominantly two types of tunneling spectra, one shows a V-shape feature which can be fitted well by a
d
-wave gap function with gap maximum of about 3.9 meV, another one exhibits a full gap of about 2.35 meV. Some spectra demonstrate mixed contributions of these two components. Combining with theoretical calculations, we attribute the
d
-wave gap to the pairing potential of the
Ni-
3
d
x
2
−
y
2
orbital. Several possible reasons are given for explaining the full gap feature. Our results indicate both similarities and distinctions between the newly found Ni-based superconductors and cuprates.
The recent observation of superconductivity in nickelate thin films has attracted a lot of attentions. Here, authors report single particle tunneling spectra on the superconducting nickelate thin films revealing two types of gap feature with one V-shape and the other a full gap.
Journal Article
Polymer Features in Crystallization
This review firstly gives an overview on the importance of crystallization in natural and synthetic polymers/macromolecules. Then it introduces the typical features that have been raised by chain-like macromolecules in crystallization, including anisotropic interactions in the thermodynamic driving forces, chain folding in the crystal morphologies, chemical confinement in the copolymer crystallization, and mechanical enhancement in the stretching processes. Four features separately cover the thermodynamics and the kinetics of polymer crystallization, as well as the crystallinity and the mechanical properties of semicrystalline polymers. The review ends up with how these features enhance specific functions of crystalline polymers, which demonstrates polymer crystallization as a challenging yet promising field in the future.
Journal Article
Discrete energy levels of Caroli-de Gennes-Matricon states in quantum limit in FeTe0.55Se0.45
Caroli-de Gennes-Matricon (CdGM) states were predicted in 1964 as low-energy excitations within vortex cores of type-II superconductors. In the quantum limit, the energy levels of these states were predicted to be discrete with the basic levels at ±
μΔ
2
/
E
F
(
μ
= 1/2, 3/2, 5/2, …) with
Δ
the superconducting energy gap and
E
F
the Fermi energy. However, due to the small ratio of
Δ
/
E
F
in most type-II superconductors, it is very difficult to observe the discrete CdGM states, but rather a symmetric peak which appears at zero bias at the vortex center. Here we report the clear observation of these discrete energy levels of CdGM states in FeTe
0.55
Se
0.45
. The rather stable energies of these bound state peaks vs. space clearly validate our conclusion. Analysis based on the energies of these CdGM states indicates that the Fermi energy in the present system is very small.
Despite predicted decades ago, the discrete Caroli-de Gennes-Matricon states are difficult to observe. Here, Chen et al. observe discrete states appearing near zero bias at the vortex center of FeTe
0.55
Se
0.45
, strongly suggesting a Caroli-de Gennes-Matricon state.
Journal Article
Electronic correlations and partial gap in the bilayer nickelate La3Ni2O7
The discovery of superconductivity with a critical temperature of about 80 K in La
3
Ni
2
O
7
single crystals under pressure has received enormous attention. La
3
Ni
2
O
7
is not superconducting under ambient pressure but exhibits a transition at
T
∗
≃ 115 K. Understanding the electronic correlations and charge dynamics is an important step towards the origin of superconductivity and other instabilities. Here, our optical study shows that La
3
Ni
2
O
7
features strong electronic correlations which significantly reduce the electron’s kinetic energy and place this system in the proximity of the Mott phase. The low-frequency optical conductivity reveals two Drude components arising from multiple bands at the Fermi level. The transition at
T
∗
removes the Drude component exhibiting non-Fermi liquid behavior, whereas the one with Fermi-liquid behavior is barely affected. These observations in combination with theoretical results suggest that the Fermi surface dominated by the Ni-
d
3
z
2
−
r
2
orbital is removed due to the transition at
T
∗
. Our experimental results provide pivotal information for understanding the transition at
T
∗
and superconductivity in La
3
Ni
2
O
7
.
The bilayer nickelate La
3
Ni
2
O
7
was recently shown to be superconducting at high-pressure. Here the authors reveal strong electronic correlations and the opening of a partial gap, providing key information for understanding the nature of the density-wavelike transition at ambient pressure and superconductivity in this compound.
Journal Article
Directly visualizing the sign change of d-wave superconducting gap in Bi2Sr2CaCu2O8+δ by phase-referenced quasiparticle interference
The superconducting state is formed by the condensation of Cooper pairs and protected by the superconducting gap. The pairing interaction between the two electrons of a Cooper pair determines the gap function. Thus, it is pivotal to detect the gap structure for understanding the mechanism of superconductivity. In cuprate superconductors, it has been well established that the gap may have a
d
-wave function. This gap function has an alternative sign change in the momentum space. It is however hard to visualize this sign change. Here we report the measurements of scanning tunneling spectroscopy in Bi
2
Sr
2
CaCu
2
O
8+δ
and conduct the analysis of phase-referenced quasiparticle interference (QPI). We see the seven basic scattering vectors that connect the octet ends of the banana-shaped contour of Fermi surface. The phase-referenced QPI clearly visualizes the sign change of the
d
-wave gap. Our results illustrate an effective way for determining the sign change of unconventional superconductors.
The superconducting gap structure contains important information to understand the pairing mechanism of unconventional superconductivity. Here, by using a newly established phase-referenced quasiparticle interference technique, the authors visualize the sign change of the
d
-wave superconducting gap directly in Bi
2
Sr
2
CaCu
2
O
8+δ
.
Journal Article
Representative Points of the Inverse Gaussian Distribution and Their Applications
The inverse Gaussian (IG) distribution, as an important class of skewed continuous distributions, is widely applied in fields such as lifetime testing, financial modeling, and volatility analysis. This paper makes two primary contributions to the statistical inference of the IG distribution. First, a systematic investigation is presented, for the first time, into three types of representative points (RPs)—Monte Carlo (MC-RPs), quasi-Monte Carlo (QMC-RPs), and mean square error RPs (MSE-RPs)—as a tool for the efficient discrete approximation of the IG distribution, thereby addressing the common scenario where practical data is discrete or requires discretization. The performance of these RPs is thoroughly examined in applications such as low-order moment estimation, density function approximation, and resampling. Simulation results demonstrate that the MSE-RPs consistently outperform the other two types in terms of approximation accuracy and robustness. Second, the Harrell–Davis (HD) and three Sfakianakis–Verginis (SV1, SV2, SV3) quantile estimators are introduced to enhance the representativeness of samples from the IG distribution, thereby significantly improving the accuracy of parameter estimation. Moreover, case studies based on real-world data confirm the effectiveness and practical utility of this quantile estimator methodology.
Journal Article
Metabolic Syndrome and Psoriasis: Mechanisms and Future Directions
Psoriasis is an immune-mediated systemic disease with associated comorbidities, including metabolic syndrome (MetS) which contributes substantially to premature mortality in patients with psoriasis. However, the pathological mechanisms underlying this comorbidity are unclear. Studies have shown that the pathological parameters of psoriasis mediate the development of MetS. We reviewed the potential mechanisms which mediate the association between psoriasis and MetS, including endoplasmic reticulum stress, pro-inflammatory cytokine releases, excess production of reactive oxygen species, alterations in adipocytokine levels and gut microbiota dysbiosis. Here, we highlight important research questions regarding this association and offer insights into MetS research and treatment.
Journal Article
Evaluation of Bisphenol A (BPA) Exposures on Prostate Stem Cell Homeostasis and Prostate Cancer Risk in the NCTR-Sprague-Dawley Rat: An NIEHS/FDA CLARITY-BPA Consortium Study
Previous work determined that early life exposure to low-dose Bisphenol A (BPA) increased rat prostate cancer risk with aging. Herein, we report on prostate-specific results from CLARITY-BPA (Consortium Linking Academic and Regulatory Insights on BPA Toxicity), which aims to resolve uncertainties regarding BPA toxicity.
We sought to
) reassess whether a range of BPA exposures drives prostate pathology and/or alters prostatic susceptibility to hormonal carcinogenesis, and
) test whether chronic low-dose BPA targets prostate epithelial stem and progenitor cells.
Sprague-Dawley rats were gavaged daily with vehicle, ethinyl estradiol (EE) or [Formula: see text] BPA/kg-BW during development or chronically, and prostate pathology was assessed at one year. One developmentally exposed cohort was given testosterone plus estradiol ([Formula: see text]) implants at day 90 to promote carcinogenesis with aging. Epithelial stem and progenitor cells were isolated by prostasphere (PS) culture from dorsolateral prostates (DLP) of rats continuously exposed for six months to [Formula: see text] BPA/kg-BW. Gene expression was analyzed by quantitative real time reverse transcription polymerase chain reaction (qRT-PCR).
Exposure to BPA alone at any dose did not drive prostate pathology. However, rats treated with EE, 2.5, 250, or [Formula: see text] BPA/kg-BW plus [Formula: see text] showed greater severity of lateral prostate intraepithelial neoplasia (PIN), and DLP ductal adenocarcinoma multiplicity was markedly elevated in tumor-bearing rats exposed to [Formula: see text]-BW. DLP stem cells, assessed by PS number, doubled with chronic EE and [Formula: see text] exposures. PS size, reflecting progenitor cell proliferation, was greater at 25 and [Formula: see text] BPA doses, which also shifted lineage commitment toward basal progenitors while reducing luminal progenitor cells.
Together, these results confirm and extend previous evidence using a rat model and human prostate epithelial cells that low-dose BPA augments prostate cancer susceptibility and alters adult prostate stem cell homeostasis. Therefore, we propose that BPA exposures may contribute to the increased carcinogenic risk in humans that occurs with aging. https://doi.org/10.1289/EHP3953.
Journal Article