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Direct observation of itinerant magnetism in the 5f-electron system UTe. PHYSICAL REVIEW LETTERS 2004; 93:267205. [PMID: 15698019 DOI: 10.1103/physrevlett.93.267205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2004] [Indexed: 05/24/2023]
Abstract
Our electron photoemission experiments demonstrate that the magnetization of the ferromagnetic state of UTe is proportional to the binding energy of the hybridized band centered around 50 meV below EF. This proportionality is direct evidence that the ferromagnetism of UTe is itinerant; i.e., the 5f electrons are not fully localized close to the atomic core. This mechanism of itinerant ferromagnetism differs from the traditional picture for 5f-electron magnetism in an essential and a novel way. We propose a simple model for the observed proportionality between the temperature dependence of the magnetization and the binding energy of the hybridized band near EF. This model allows us to estimate the effective magnetic interaction and to identify signatures of itinerant ferromagnetism in other materials.
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Abstract
Complementary angle-resolved photoemission and bulk-sensitive k-resolved resonant inelastic x-ray scattering of divalent hexaborides reveal a >1 eV X-point gap between the valence and conduction bands, in contradiction to the band overlap assumed in several models of their novel ferromagnetism. This semiconducting gap implies that carriers detected in transport measurements arise from defects, and the measured location of the bulk Fermi level at the bottom of the conduction band implicates boron vacancies as the origin of the excess electrons. The measured band structure and X-point gap in CaB6 additionally provide a stringent test case for many-body quasiparticle band calculations.
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Spontaneous breaking of time-reversal symmetry in the pseudogap state of a high-Tc superconductor. Nature 2002; 416:610-3. [PMID: 11948344 DOI: 10.1038/416610a] [Citation(s) in RCA: 252] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A change in 'symmetry' is often observed when matter undergoes a phase transition-the symmetry is said to be spontaneously broken. The transition made by underdoped high-transition-temperature (high-Tc) superconductors is unusual, in that it is not a mean-field transition as seen in other superconductors. Rather, there is a region in the phase diagram above the superconducting transition temperature Tc (where phase coherence and superconductivity begin) but below a characteristic temperature T* where a 'pseudogap' appears in the spectrum of electronic excitations. It is therefore important to establish if T* is just a cross-over temperature arising from fluctuations in the order parameter that will establish superconductivity at Tc (refs 3, 4), or if it marks a phase transition where symmetry is spontaneously broken. Here we report that, for a material in the pseudogap state, left-circularly polarized photons give a different photocurrent from right-circularly polarized photons. This shows that time-reversal symmetry is spontaneously broken below T*, which therefore corresponds to a phase transition.
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Non-fermi liquid angle resolved photoemission line shapes of li0. 9Mo6O17. PHYSICAL REVIEW LETTERS 2000; 85:3985. [PMID: 11041982 DOI: 10.1103/physrevlett.85.3985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/1999] [Indexed: 05/23/2023]
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Photoelectron spectroscopy of strongly correlated Yb compounds. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:17515-17535. [PMID: 9985876 DOI: 10.1103/physrevb.54.17515] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Complete band-structure determination of the quasi-two-dimensional Fermi-liquid reference compound TiTe2. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:2453-2465. [PMID: 9986092 DOI: 10.1103/physrevb.54.2453] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Valence-band dispersion in angle-resolved resonant photoemission from LaSb. PHYSICAL REVIEW LETTERS 1996; 76:4265-4268. [PMID: 10061243 DOI: 10.1103/physrevlett.76.4265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Electronic band dispersion and pseudogap in quasicrystals: Angular-resolved photoemission studies on icosahedral Al70Pd21.5Mn8.5. PHYSICAL REVIEW LETTERS 1995; 75:4540-4543. [PMID: 10059934 DOI: 10.1103/physrevlett.75.4540] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Electronic states and stability of the insulating RbC60 dimer phase. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:11662-11664. [PMID: 9980295 DOI: 10.1103/physrevb.52.r11662] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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11
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Photoemission study of valence electrons in La(Co1-xFex)13 (x=0,0.2). PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:4360-4365. [PMID: 9981567 DOI: 10.1103/physrevb.52.4360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Electronic structure as a function of doping in YBa2Cu3Ox(6.2 <= x <= 6.9) studied by angle-resolved photoemission. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:553-558. [PMID: 9979634 DOI: 10.1103/physrevb.52.553] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Enhanced Fe 3d spectral weight near the Fermi level in Fe overlayers on Cr. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:1039-1044. [PMID: 9978254 DOI: 10.1103/physrevb.51.1039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Band dispersion in C60(111): An angle-resolved photoemission study. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:11239-11242. [PMID: 9975247 DOI: 10.1103/physrevb.50.11239] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Hybridization and correlation effects in the photoemission spectra of RNi2 (R=Ce, Pr, and Nd). PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 49:16248-16255. [PMID: 10010771 DOI: 10.1103/physrevb.49.16248] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Photoemission study of Ce-catalyzed oxidation of W(110) and W(111). PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:12178-12182. [PMID: 10007569 DOI: 10.1103/physrevb.48.12178] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Electronic and magnetic structures of the rare-earth permanent magnet Nd2Fe14B. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:6217-6224. [PMID: 10009165 DOI: 10.1103/physrevb.48.6217] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Luttinger Fermi surface of metallic gap spectral weight in Nd1.85Ce0.15CuO4-y. PHYSICAL REVIEW LETTERS 1993; 70:3163-3166. [PMID: 10053791 DOI: 10.1103/physrevlett.70.3163] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Photoemission study of RCo2 (R=Ce, Pr, Nd). PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 46:15689-15696. [PMID: 10003709 DOI: 10.1103/physrevb.46.15689] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Fermi-surface topology of YBa2Cu3Ox with varied oxygen stoichiometry: A photoemission study. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 46:11056-11068. [PMID: 10002970 DOI: 10.1103/physrevb.46.11056] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Fermi-liquid line shapes measured by angle-resolved photoemission spectroscopy on 1-T-TiTe2. PHYSICAL REVIEW LETTERS 1992; 69:808-811. [PMID: 10047038 DOI: 10.1103/physrevlett.69.808] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Electronic structure near EF in YBa2Cu3Ox for 6.35 <= x <= 6.9: A photoemission study. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 45:5614-5621. [PMID: 10000279 DOI: 10.1103/physrevb.45.5614] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Valence bands and Fermi-surface topology of untwinned single-crystal YBa2Cu3O6.9. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 45:5563-5576. [PMID: 10000275 DOI: 10.1103/physrevb.45.5563] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Evidence of chemical-potential shift with hole doping in Bi2Sr2CaCu2O8+ delta. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 44:12098-12101. [PMID: 9999363 DOI: 10.1103/physrevb.44.12098] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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" gamma - alpha " phase transition of monolayer Ce on W(110). PHYSICAL REVIEW LETTERS 1991; 67:1622-1625. [PMID: 10044202 DOI: 10.1103/physrevlett.67.1622] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Angle-resolved-photoemission study of Bi2Sr2CaCu2O8+ delta : Metallicity of the Bi-O plane. PHYSICAL REVIEW LETTERS 1990; 65:3056-3059. [PMID: 10042768 DOI: 10.1103/physrevlett.65.3056] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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High-resolution angle-resolved photoemission study of the Fermi surface and the normal-state electronic structure of Bi2Sr2CaCu2O8. PHYSICAL REVIEW. B, CONDENSED MATTER 1990; 42:381-386. [PMID: 9994550 DOI: 10.1103/physrevb.42.381] [Citation(s) in RCA: 218] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Resonant photoemission study of Nd2-xCexCuO4-y: Nature of electronic states near the Fermi level. PHYSICAL REVIEW LETTERS 1990; 64:595-598. [PMID: 10042024 DOI: 10.1103/physrevlett.64.595] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Abstract
Superconductivity is related to the presence of a narrow forbidden gap in the spectrum of the possible energies for the electrons in the material. These "superconductivity gaps" have traditionally been studied with tunneling and infrared absorption experiments. A third, powerful technique has been made possible by the discovery of hightransition temperature materials: the direct observation of the gap in photoemission spectra. The data analysis requires a careful reconsideration of the standard Einstein-Fermi model of the photoelectric effect. The conclusions are surprisingly simple and offer an alternate way to measure superconductivity gaps. This approach can also be used to study the directional properties of the gap, phenomena related to the coherence length, and possible departures from Fermi-liquid behavior.
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Superconducting Gap in Bi-Sr-Ca-Cu-O by High-Resolution Angle-Resolved Photoelectron Spectroscopy. Science 1989; 245:731-3. [PMID: 17791711 DOI: 10.1126/science.245.4919.731] [Citation(s) in RCA: 354] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Detailed studies indicate a superconducting gap in the high-temperature superconductor Bi(2)Sr(2)CaCu(2)O(8). Photoemission measurements with high energy and angle resolution isolate the behavior of a single band as it crosses the Fermi level in both the normal and superconducting states, giving support to the Fermi liquid picture. The magnitude of the gap is 24 millielectron volts.
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Large, dispersive photoelectron Fermi edge and the electronic structure of YBa2Cu3O6.9 single crystals measured at 20 K. PHYSICAL REVIEW. B, CONDENSED MATTER 1989; 40:2268-2277. [PMID: 9992108 DOI: 10.1103/physrevb.40.2268] [Citation(s) in RCA: 95] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Ba 4d core-level spectroscopy in the YBa2Cu3O6.9 high-Tc superconductor: Existence of a surface-shifted component. PHYSICAL REVIEW. B, CONDENSED MATTER 1989; 40:2650-2653. [PMID: 9992178 DOI: 10.1103/physrevb.40.2650] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Imaging of 5f densities of states in resonant photoemission measurements. PHYSICAL REVIEW. B, CONDENSED MATTER 1988; 38:1627-1631. [PMID: 9946443 DOI: 10.1103/physrevb.38.1627] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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La 4d-->4f resonance absorption in LaF3: Temperature dependence. PHYSICAL REVIEW. B, CONDENSED MATTER 1987; 35:7658-7662. [PMID: 9941073 DOI: 10.1103/physrevb.35.7658] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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