| 1. |
- Carlsson, Anna K, 1966, et al.
(author)
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High-resolution photoemission from a tunable quantum well: Cu(111)/Na
- 1997
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In: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 56:3, s. 1593 - 1600
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Journal article (peer-reviewed)abstract
- High-resolution photoemission (ΔE=5 meV) at a low photon energy (3.82 eV) is used to probe discrete quantum-well-type subband states near, below, and above EF for Cu(111) covered with 2 ML or less of Na. A subband characteristic of the monolayer range shifts gradually to lower energy as the coverage is increased, extending below the Fermi level for coverages above 0.85 ML. Combined with previous observations of shifts for filled and empty states the present results show that the Na monolayer has continuously tunable quantum-well state energies. Beyond the monolayer range quantum-well states characteristic of both one and two atomic layers are observed, indicating growth of the second layer via monolayer high islands. A small downshift, by 25 meV, with increasing coverage in the second layer is ascribed to an increase of the island size. Lorentzian photoemission line shapes are observed for well-ordered samples. The linewidth varies linearly with temprature in the probed range (130–295 K) and this is ascribed to the phonon contribution to the width. Structural disorder leads to an asymmetric line, which is Lorentzian on the steeper, low-kinetic-energy side.
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| 2. |
- Carlsson, Anna K, 1966, et al.
(author)
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Observation of structure changes for Li/Cu(111) by photoemission from Li core and quantum-well states
- 1998
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In: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 57:20, s. 13192 - 13198
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Journal article (peer-reviewed)abstract
- Via photoemission from discrete quantum-well valence states and the Li 1s core level, three different types of atom rearrangements are observed for Cu(111)/Li. In the monolayer coverage range gradual energy shifts for the core-level as well as a quantum-well state reflect a gradual lateral compression of the Li overlayer as more atoms are adsorbed. The onset of Li substitution and formation of a (2×2) structure when, at RT, monolayer Li coverage is exceeded, is monitored via the disappearance and appearance of quantum-well states characteristic of the adsorbed full monolayer of Li and the part substitutional (2×2) structure, respectively. A splitting of the Li 1s emission peak into a doublet reflects the two different Li sites characteristic of the (2×2) phase. A small energy shift of the quantum-well state (25 meV) indicates that, if it is cooled (170 K), the substitutional structure is unstable with respect to Li adsorption.
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| 3. |
- Carlsson, Anna K, 1966, et al.
(author)
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Oscillatory photoemission cross section for simple-metal quantum wells
- 1995
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In: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 52:15, s. 11144 - 11146
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Journal article (peer-reviewed)abstract
- A strong, oscillatory photon energy dependence is observed for the intensity of photoemission peaks due to quantum-well states in Na overlayers on Cu(111). The measurements are made at low photon energies (hν
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| 4. |
- Carlsson, Anna K, 1966, et al.
(author)
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Shifts and widths of metal-overlayer quantum-well states near EF observed by photoemission
- 1994
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In: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 50:12, s. 8926 - 8929
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Journal article (peer-reviewed)abstract
- Photoelectron energy spectra reveal discrete valence-electron states in the range 0–220 meV above EF for 1–3 atomic layers of Na on Cu(111). Apart from a stepwise dependence on the number of atomic Na layers the energy of the quantum-well states depends in a gradual manner on how full the layer is. The states are as well defined in energy as comparable surface states producing peak widths (50–90 meV), which depend on temperature and coverage.
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| 5. |
- Gatt, Rafael, 1960, et al.
(author)
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Pressure effect in the Hg-based superconductors: A structural study
- 1998
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In: Physical Review B. - 2469-9969 .- 2469-9950. ; 57:21, s. 13922-13928
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Journal article (peer-reviewed)abstract
- Energy-dispersive synchrotron x-ray-diffraction studies were performed on powder samples of Hg1212 and Hg1223 in a diamond-anvil cell at pressure up to 300 kbar. High compressibility was found. A reversible structural transition was observed, which is suggested to correspond to a pressure-induced ordering along the c axis. The accommodation of the Ba ion at high pressure is studied, and the effect it might have on the electronic structure of these materials is discussed by employing results from cluster calculations.
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| 6. |
- Gershenson, M. E., et al.
(author)
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Nonlocal effects in the resistance of one-dimensional wires with dangling side branches
- 1995
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In: Physical Review B. - 2469-9969 .- 2469-9950. ; 51, s. 10256-9
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Journal article (peer-reviewed)abstract
- We have studied the quantum corrections to the resistance of one-dimensional gold wires with periodically spaced dangling side branches. Both the weak localization and interaction corrections to the resistance of such samples are strongly reduced when the distance between branches becomes smaller than the quantum length scales. The dependence of the quantum corrections on the distance between the branches then becomes a measurement of the quantum lengths
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| 7. |
- Koblishka, M. R., et al.
(author)
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Flux penetration into an artificially granular high-Tc superconductor
- 1999
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In: Physical Review B. - 2469-9969 .- 2469-9950. ; 59, s. 12114-20
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Journal article (peer-reviewed)abstract
- A YBa2Cu3O7- thin film is patterned into a hexagonal close-packed lattice of disks (2r=50 m) which are touching each other at the circumferences in order to enable the flow of an intergranular current. Such a sample was suggested by Koblischka et al. [Appl. Phys. Lett. 70, 514 (1997)] as a model for a layered granular structure like in a (Pb,Bi)2Sr2Ca2Cu3O10+ (Bi-2223) tape. The magnetization measurements reveal an anomalous position of the low-field peak (central peak) similar to Bi-2223 tapes. Magneto-optic imaging is employed to visualize the local-field distributions. At low magnification, the flux patterns in the intergranular area between the disks are observed. The observations at high magnification reveal the flux penetration and pinning within the disks. It is shown that such samples may serve as model samples for granular high-Tc superconductors
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| 8. |
- Lindgren, Stig-Åke, 1950, et al.
(author)
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Coverage-dependent frequency for Li-atom vibrations on Cu(111)
- 1996
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In: Physical Review B. - 2469-9969 .- 2469-9950. ; 54:15, s. 10912 - 10916
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Journal article (peer-reviewed)abstract
- Electron-energy-loss spectra recorded for monolayer amounts of Li adsorbed on Cu(111) show a loss peak associated with Li vibrations perpendicular to the substrate. The loss energy shifts from 38 meV at low coverage to 43 meV at 0.3 ML and remains constant for coverages between 0.3 and 0.5 ML. The loss intensity passes a maximum at a Li coverage of 0.15 ML and gradually decreases such that it is difficult to resolve a loss peak at coverages above 0.5 ML. The high loss energy indicates that the adatom resides on the surfaces rather than in substitutional sites. The frequency shift is much too large to be explained by dipole-dipole interactions. The above results are obtained with the evaporation source loaded with the natural Li isotope mixture (92.6% 7Li, 7.4% 6Li). Measurements with 6Li show that the increase of the vibration frequency with increasing coverage is not an isotope effect.
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