120 research outputs found
Fermi Surface and Band Renormalization in (Sr,K)FeAs Superconductor from Angle-Resolved Photoemission Spectroscopy
High resolution angle-resolved photoemission measurements have been carried
out on (Sr,K)FeAs superconductor (Tc=21 K). Three hole-like Fermi
surface sheets are clearly resolved for the first time around the Gamma point.
The overall electronic structure shows significant difference from the band
structure calculations. Qualitative agreement between the measured and
calculated band structure is realized by assuming a chemical potential shift of
-0.2 eV. The obvious band renormalization suggests the importance of electron
correlation in understanding the electronic structure of the Fe-based
compounds.Comment: 4 pages, 4 figure
Cu doping effects on the electronic structure of Fe1-xCuxSe
Using angle-resolved photoemission spectroscopy (ARPES), we studied the
evolution of the electronic structure of Fe1-xCuxSe from x = 0 to 0.10. We
found that the Cu dopant introduces extra electron carriers. The hole bands
near the gamma point are observed to steadily shift downward with increasing
doping and completely sink down below the Fermi level (EF) for x > 0.05.
Meanwhile, the electron pocket near the M point becomes larger but loses the
spectral weight near EF. We also observed that effective mass of the electron
band near the M point increases with doping. Our result explains why
superconductivity disappears and metal insulator transition (MIT) like behavior
occurs upon Cu doping in terms of electronic structure, and provide insight
into emergent magnetic fluctuation in Fe1-xCuxSe
Ubiquitous conservative interaction patterns between post-spliced introns and their mRNAs revealed by genome-wide interspecies comparison
Introns, as important vectors of biological functions, can influence many stages of mRNA metabolism. However, in recent research, post-spliced introns are rarely considered. In this study, the optimal matched regions between introns and their mRNAs in nine model organism genomes were investigated with improved Smith–Waterman local alignment software. Our results showed that the distributions of mRNA optimal matched frequencies were highly consistent or universal. There are optimal matched frequency peaks in the UTR regions, which are obvious, especially in the 3′-UTR. The matched frequencies are relatively low in the CDS regions of the mRNA. The distributions of the optimal matched frequencies around the functional sites are also remarkably changed. The centers of the GC content distributions for different sequences are different. The matched rate distributions are highly consistent and are located mainly between 60% and 80%. The most probable value of the optimal matched segments is about 20 bp for lower eukaryotes and 30 bp for higher eukaryotes. These results show that there are abundant functional units in the introns, and these functional units are correlated structurally with all kinds of sequences of mRNA. The interaction between the post-spliced introns and their corresponding mRNAs may play a key role in gene expression
Monotonic d-wave Superconducting Gap in Optimally-Doped BiSrLaCuO Superconductor by Laser-Based Angle-Resolved Photoemission Spectroscopy
The momentum and temperature dependence of the superconducting gap and
pseudogap in optimally-doped BiSrLaCuO superconductor
is investigated by super-high resolution laser-based angle-resolved
photoemission spectroscopy. The measured energy gap in the superconducting
state exhibits a standard {\it d}-wave form. Pseudogap opens above T over a
large portion of the Fermi surface with a "Fermi arc" formed near the nodal
region. In the region outside of the "Fermi arc", the pseudogap has the similar
magnitude and momentum dependence as the gap in the superconducting state which
changes little with temperature and shows no abrupt change across T. These
observations indicate that the pseudogap and superconducting gap are closely
related and favor the picture that the pseudogap is a precursor to the
superconducting gap.Comment: 4 pages, 4 figure
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