| 1. |
- Shi, Ming, et al.
(författare)
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Coherent d-wave superconducting gap in underdoped La2-xSrxCuO4 by angle-resolved photoemission spectroscopy
- 2008
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 101:4, s. 047002-
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Tidskriftsartikel (refereegranskat)abstract
- We present angle-resolved photoemission spectroscopy data on moderately underdoped La1.855Sr0.145CuO4 at temperatures below and above the superconducting transition temperature. Unlike previous studies of this material, we observe sharp spectral peaks along the entire underlying Fermi surface in the superconducting state. These peaks trace out an energy gap that follows a simple d-wave form, with a maximum superconducting gap of 14 meV. Our results are consistent with a single gap picture for the cuprates. Furthermore our data on the even more underdoped sample La1.895Sr0.105CuO4 also show sharp spectral peaks, even at the antinode, with a maximum superconducting gap of 26 meV.
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| 2. |
- Shi, M., et al.
(författare)
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Spectroscopic evidence for preformed Cooper pairs in the pseudogap phase of cuprates
- 2009
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 88:2
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Tidskriftsartikel (refereegranskat)abstract
- Angle-resolved photoemission on underdoped La1.895Sr0.105CuO4 reveals that in the pseudogap phase, the dispersion has two branches located above and below the Fermi level with a minimum at the Fermi momentum. This is characteristic of the Bogoliubov dispersion in the superconducting state. We also observe that the superconducting and pseudogaps have the same d-wave form with the same amplitude. Our observations provide direct evidence for preformed Cooper pairs, implying that the pseudogap phase is a precursor to superconductivity.
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| 3. |
- Chang, Johan, et al.
(författare)
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Anisotropic quasiparticle scattering rates in slightly underdoped to optimally doped high-temperature La2-xSrxCuO4 superconductors
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:20, s. 205103-
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Tidskriftsartikel (refereegranskat)abstract
- An angle-resolved photoemission study of the scattering rate in the superconducting phase of the high-temperature superconductor La2-xSrxCuO4 with x=0.145 and x=0.17, as a function of binding energy and momentum, is presented. We observe that the scattering rate scales linearly with binding energy up to the high-energy scale E-1 similar to 0.4 eV. The scattering rate is found to be strongly anisotropic, with a minimum along the (0,0)-(pi,pi) direction. A possible connection to a quantum-critical point is discussed.
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| 4. |
- Chang, J., et al.
(författare)
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Electronic structure near the 1/8-anomaly in La-based cuprates
- 2008
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- We report an angle-resolved photoemission study of the electronic structure of the pseudogap state in La1.48Nd0.4Sr0.12CuO4 (T-c < 7 K). Two opposite dispersing Fermi arcs are the main result of this study. Several scenarios that can explain this observation are discussed.
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| 5. |
- Chang, Johan, et al.
(författare)
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When low- and high-energy electronic responses meet in cuprate superconductors
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:22, s. 224508-
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Tidskriftsartikel (refereegranskat)abstract
- The existence of coherent quasiparticles near the Fermi energy in the low-temperature state of high-temperature superconductors has been well established by angle-resolved photoemission spectroscopy (ARPES). We present a study of La1.83Sr0.17CuO4 in the superconducting state and report an abrupt change in the quasiparticle spectral function, as we follow the dispersion of the ARPES signal from the Fermi energy to 0.6 eV. The interruption in the quasiparticle dispersion separates coherent quasiparticle peaks at low energies from broad incoherent excitations at high energies. We find that the boundary between these low-energy and high-energy features exhibits a cosine-shaped momentum dependence, reminiscent of the superconducting d-wave gap. Further intriguing similarities between characteristics of the incoherent excitations and quasiparticle properties suggest a close relation between the electronic response at high and low energies in cuprate superconductors.
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| 6. |
- Hertz, Hans M., et al.
(författare)
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Laboratory x-ray micro imaging : Sources, optics, systems and applications
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186
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Tidskriftsartikel (refereegranskat)abstract
- We summarize the recent progress in laboratory-scale soft and hard x-ray micro imaging in Stockholm. Our soft x-ray work is based on liquid-jet laser-plasma sources which are combined with diffractive and multilayer optics to form laboratory x-ray microscopes. In the hard x-ray regime the imaging is based on a liquid-metal-jet electron-impact source which provides the necessary coherence to allow phase-contrast imaging with high fidelity.
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| 7. |
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| 8. |
- Mudry, JM, et al.
(författare)
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Insulin and Glucose Alter Death-Associated Protein Kinase 3 (DAPK3) DNA Methylation in Human Skeletal Muscle
- 2017
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 66:3, s. 651-662
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Tidskriftsartikel (refereegranskat)abstract
- DNA methylation is altered by environmental factors. We hypothesized that DNA methylation is altered in skeletal muscle in response to either insulin or glucose exposure. We performed a genome-wide DNA methylation analysis in muscle from healthy men before and after insulin exposure. DNA methylation of selected genes was determined in muscle from healthy men and men with type 2 diabetes before and after a glucose tolerance test. Insulin altered DNA methylation in the 3′ untranslated region of the calcium pump ATP2A3 gene. Insulin increased DNA methylation in the gene body of DAPK3, a gene involved in cell proliferation, apoptosis, and autophagy. DAPK3 methylation was reduced in patients with type 2 diabetes. Carbohydrate ingestion reduced DAPK3 DNA methylation in healthy men and men with type 2 diabetes, suggesting glucose may play a role. Supporting this, DAPK3 DNA methylation was inversely correlated with the 2-h glucose concentration. Whereas glucose incorporation to glycogen was unaltered by small interfering RNA against DAPK3, palmitate oxidation was increased. In conclusion, insulin and glucose exposure acutely alter the DNA methylation profile of skeletal muscle, indicating that DNA methylation constitutes a rapidly adaptive epigenetic mark. Furthermore, insulin and glucose modulate DAPK3 DNA methylation in a reciprocal manner, suggesting a feedback loop in the control of the epigenome.
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