FeSe layer-based superconductors exhibit exotic and distinctive properties. The undoped FeSe shows nematicity and superconductivity, while the heavily electron-doped KxFe2−ySe2 and single-layer FeSe/SrTiO3 possess high superconducting transition temperatures that pose theoretical challenges. However, a comprehensive study on the doping dependence of an FeSe layer-based superconductor is still lacking due to the lack of a clean means of doping control. Through angle-resolved photoemission spectroscopy studies on K-dosed thick FeSe films and FeSe0.93S0.07 bulk crystals, here we reveal the internal connections between these two types of FeSe-based superconductors, and obtain superconductivity below ∼46 K in an FeSe layer under electron doping without interfacial effects. Moreover, we discover an exotic phase diagram of FeSe with electron doping, including a nematic phase, a superconducting dome, a correlation-driven insulating phase and a metallic phase. Such an anomalous phase diagram unveils the remarkable complexity, and highlights the importance of correlations in FeSe layer-based superconductors.
In patients who remain comatose after cardiac arrest, quantitative DWI MRI findings correlate with early recovery of consciousness. A DWI MRI threshold of 650 × 10(-6) mm(2)/s in ≥10% of brain volume can differentiate patients with good versus poor outcome, though in this patient population the threshold was not 100% specific for poor outcome.
Recently, superconductivity in potassium (K) doped p-terphenyl (C18H14) has been suggested by the possible observation of the Meissner effect and subsequent photoemission spectroscopy measurements, but the detailed lattice structure and more-direct evidence are still lacking. Here we report a low temperature scanning tunneling microscopy/spectroscopy (STM/STS) study on K-doped single layer pterphenyl films grown on Au (111). We observe several ordered phases with different morphologies and electronic behaviors, in two of which a sharp and symmetric low-energy gap of about 11 meV opens below 50 K. In particular, the gap shows no obvious response to a magnetic field up to 11 Tesla, which would caution against superconductivity as an interpretation in previous reports of Kdoped p-terphenyl materials. Such gapped phases are rarely (if ever) observed in single layer hydrocarbon molecular crystals. Our work also paves the way for fabricating doped two-dimensional (2D) hydrocarbon materials, which will provide a platform to search for novel emergent phenomena.Organic molecular materials provide an important playground in condensed matter physics, exhibiting charge density wave (CDW) phases [1], anti-ferromagnetism [1-3], Mott-insulating state [1-3] and superconductivity [2-9]. Among these, organic superconductors are of particular interest for their theoretically predicted high critical temperatures [10]. Known organic superconductors include graphite intercalation compounds [4,5], alkali-metal doped fullerenes [2, 3], organic salts [1, 6] and alkalimetal doped aromatic hydrocarbon molecular crystals [7-9]. The record for the superconducting transition temperature (Tc) in the organic superconductors has long been 38 K for doped fullerene (Cs3C60 under high pressure) [2, 3] with minimal further progress obtained thereafter. Recently, reports of low-temperature diamagnetism up to 120 K in K-doped para-terphenyl (p-terphenyl or PTP) rekindled the interest for exploring possible high temperature superconductivity in doped aromatic hydrocarbon molecular crystals [11]. p-Terphenyl consists of three benzene rings linked by single C-C bonds in the para position. By doping K into p-terphenyl molecular crystals, Wang et al. observed a weak Meissner-like effect below 7.2 K, 43 K and 120 K for different doping levels [11][12][13][14]. Shortly thereafter, a gap persisting up to at least 60 K was observed in surface K-dosed p-terphenyl crystals by photoemission spectroscopy [15]. Taken together, these indicate possible high-temperature superconductivity in electron-doped p-terphenyl. However, since the reported diamagnetic signal is very low, corresponding to less than a 0.1% superconducting shielding fraction, further experiments on structural characterization and electronic properties are essential to clarify the origin of these unique phenomena.Here, via high vacuum deposition, we have grown well-ordered (K-doped) p-terphenyl films on Au (111). A clear low energy gap of about 11-13 meV is observed in two of the ordered phases, but...
Adipokinetic hormones (AKHs), the neurohormones synthesized in the insect corpora cardiaca are known to mobilize lipids and carbohydrates for energyconsuming activities including reproduction. However, both inhibitory and stimulatory effects of AKHs on insect reproduction have been reported, and the underlying mechanisms remain elusive. Using the migratory locust, Locusta migratoria, as a model system, we report here that AKHs are expressed in response to rhythmic diel change, and AKH III expression increases markedly at photophase. Diurnal injection of AKH III but not AKH I or AKH II in adult females stimulates vitellogenesis and egg development. In contrast, AKH treatment at scotophase represses female reproduction. RNA interference-mediated knockdown of AKH receptor (AKHR) results in significantly reduced vitellogenin (Vg) expression in the fat body at photophase along with reduced Vg deposition in the ovary. AKHR knockdown also leads to decreased expression of Brummer, triacylglycerol lipase and trehalose transporter, accompanied by suppressed mobilization of triacylglycerol and trehalose. We propose that in addition to stimulating Vg expression at photophase, AKH/AKHR signalling is likely to regulate ovarian uptake of Vg via triacylglycerol mobilization and trehalose homeostasis. This study provides new insights into the understanding of AKH/AKHR signalling in the regulation of insect reproduction.
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