76
|
Ho YP, Reddy PM, Chen CT, Lo AA. Mass Spectrometry in Microbial Forensics. FORENSIC SCIENCE REVIEW 2009; 21:25-50. [PMID: 26242239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Mass spectrometry (MS) has become a powerful tool to identify microbial biomarkers. Rapid and reliable identification of microorganisms by MS without extensive sample pretreatment is now possible. An effective microbial forensics program requires accurate characterization of pathogens to indicate their presence. MS methods provide such capabilities for forensic analysis. MS methods currently utilized for microbial analyses are reviewed. Techniques including capillary electrophoresis, liquid chromatography, gas chromatography, and pyrolysis that are coupled to MS analysis are described. A brief introduction to the two advanced ionization techniques, electrospray ionization and matrix-assisted laser desorption/ionization, for MS is provided in this review. Methods based on characterization of biomarkers including proteins, DNA molecules, lipids, and other small molecules are reviewed.
Collapse
|
77
|
Chi CC, Chiang CL, Liu SW, Yueh H, Chen CT, Chen CT. Achieving high-efficiency non-doped blue organic light-emitting diodes: charge-balance control of bipolar blue fluorescent materials with reduced hole-mobility. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b902910a] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
78
|
Hsu FM, Chien CH, Hsieh YJ, Wu CH, Shu CF, Liu SW, Chen CT. Highly efficient red electrophosphorescent device incorporating a bipolar triphenylamine/bisphenylsulfonyl-substituted fluorene hybrid as the host. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b910292b] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
79
|
Huang SW, Huang DJ, Okamoto J, Mou CY, Wu WB, Yeh KW, Chen CL, Wu MK, Hsu HC, Chou FC, Chen CT. Magnetic ground state and transition of a quantum multiferroic LiCu2O2. PHYSICAL REVIEW LETTERS 2008; 101:077205. [PMID: 18764576 DOI: 10.1103/physrevlett.101.077205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2008] [Indexed: 05/26/2023]
Abstract
Based on resonant soft x-ray magnetic scattering, we report that LiCu2O2 exhibits a large interchain coupling which suppresses quantum fluctuations along spin chains, and a quasi-2D short-range magnetic order prevails at temperatures above the magnetic transition. These observations unravel the fact that the ground state of LiCu2O2 possesses long-range 2D-like incommensurate magnetic order rather than being a gapped spin liquid as expected from the nature of quantum spin-1/2 chains. In addition, the spin coupling along the c axis is found to be essential for inducing electric polarization.
Collapse
|
80
|
Hossain MA, Hu Z, Haverkort MW, Burnus T, Chang CF, Klein S, Denlinger JD, Lin HJ, Chen CT, Mathieu R, Kaneko Y, Tokura Y, Satow S, Yoshida Y, Takagi H, Tanaka A, Elfimov IS, Sawatzky GA, Tjeng LH, Damascelli A. Crystal-field level inversion in lightly Mn-doped Sr3Ru2O7. PHYSICAL REVIEW LETTERS 2008; 101:016404. [PMID: 18764131 DOI: 10.1103/physrevlett.101.016404] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2008] [Indexed: 05/26/2023]
Abstract
Sr3(Ru(1-x)Mnx)2O7, in which 4d-Ru is substituted by the more localized 3d-Mn, is studied by x-ray dichroism and spin-resolved density functional theory. We find that Mn impurities do not exhibit the same 4+ valence of Ru, but act as 3+ acceptors; the extra eg electron occupies the in-plane 3d(x2-y2) orbital instead of the expected out-of-plane 3d(3z2-r2). We propose that the 3d-4d interplay, via the ligand oxygen orbitals, is responsible for this crystal-field level inversion and the material's transition to an antiferromagnetic, possibly orbitally ordered, low-temperature state.
Collapse
|
81
|
Hansmann P, Severing A, Hu Z, Haverkort MW, Chang CF, Klein S, Tanaka A, Hsieh HH, Lin HJ, Chen CT, Fåk B, Lejay P, Tjeng LH. Determining the crystal-field ground state in rare earth heavy fermion materials using soft-x-ray absorption spectroscopy. PHYSICAL REVIEW LETTERS 2008; 100:066405. [PMID: 18352496 DOI: 10.1103/physrevlett.100.066405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2007] [Indexed: 05/26/2023]
Abstract
We infer that soft-x-ray absorption spectroscopy is a versatile method for the determination of the crystal-field ground state symmetry of rare earth heavy fermion systems, complementing neutron scattering. Using realistic and universal parameters, we provide a theoretical mapping between the polarization dependence of Ce M(4,5) spectra and the charge distribution of the Ce 4f states. The experimental resolution can be orders of magnitude larger than the 4f crystal-field splitting itself. To demonstrate the experimental feasibility of the method, we investigated CePd2Si2, thereby settling an existing disagreement about its crystal-field ground state.
Collapse
|
82
|
Chen CT, Kanai T, Wang XY, Zhu Y, Watanabe S. High-average-power light source below 200 nm from a KBe(2)BO(3)F(2) prism-coupled device. OPTICS LETTERS 2008; 33:282-284. [PMID: 18246155 DOI: 10.1364/ol.33.000282] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Using a 2.3 mm thick KBe(2)BO(3)F(2) crystal optically contacted with CaF(2) in a prism-coupled device, we have obtained an average output power of as much as 360 mW at 200 nm. Long-term stability was verified above a 150 mW level at 200 nm. An output power of 50 mW was also obtained with a narrow spectral width of 0.007 pm at 193.5 nm.
Collapse
|
83
|
Baba T, Yokoya T, Tsuda S, Kiss T, Shimojima T, Ishizaka K, Takeya H, Hirata K, Watanabe T, Nohara M, Takagi H, Nakai N, Machida K, Togashi T, Watanabe S, Wang XY, Chen CT, Shin S. Bulk electronic structure of the antiferromagnetic superconducting phase in ErNi2B2C. PHYSICAL REVIEW LETTERS 2008; 100:017003. [PMID: 18232808 DOI: 10.1103/physrevlett.100.017003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2006] [Indexed: 05/25/2023]
Abstract
We have performed temperature- (T-)dependent laser-photoemission spectroscopy of the antiferromagnetic (AF) superconductor ErNi2B2C to study the electronic-structure evolution reflecting the interplay between antiferromagnetism and superconductivity. The spectra at the superconducting (SC) phase show a very broad spectral shape. A T-dependent SC gap shows a sudden deviation from the BCS prediction just below TN. This observation can be explained well by the theoretical model and thus represents the characteristic bulk electronic structure of the AF SC phase for the first time.
Collapse
|
84
|
Lee RH, Hsu HF, Chan LH, Chen CT. Enhancing the electroluminescence performances of blue polymer light emitting devices via carriers transporting materials incorporation. J Appl Polym Sci 2008. [DOI: 10.1002/app.28384] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
85
|
Lee YT, Chiang CL, Chen CT. Solid-state highly fluorescent diphenylaminospirobifluorenylfumaronitrile red emitters for non-doped organic light-emitting diodes. Chem Commun (Camb) 2008:217-9. [DOI: 10.1039/b711157f] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
86
|
Shimojima T, Shibata Y, Ishizaka K, Kiss T, Chainani A, Yokoya T, Togashi T, Wang XY, Chen CT, Watanabe S, Yamaura J, Yonezawa S, Muraoka Y, Hiroi Z, Saitoh T, Shin S. Interplay of superconductivity and rattling phenomena in beta-pyrochlore KOs2O6 studied by photoemission spectroscopy. PHYSICAL REVIEW LETTERS 2007; 99:117003. [PMID: 17930463 DOI: 10.1103/physrevlett.99.117003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2006] [Indexed: 05/25/2023]
Abstract
The electronic structure near the Fermi level (EF) of the beta-pyrochlore superconductor KOs2O6 is studied using laser-excited ultrahigh-resolution photoemission spectroscopy. The superconducting gap clearly opens across the superconducting transition (Tc=9.6 K), with the strong electron-phonon coupling value of 2Delta(0)/k B Tc>or=4.56. A fitting analysis identifies clear anomalies at Tp=7.5 K in the temperature dependencies of the superconducting gap size and the quasiparticle relaxation lifetime. These anomalies and the fine spectral structures arising from phonons suggest that the existence of the rattling behavior of K ions significantly affects the superconductivity in KOs2O6.
Collapse
|
87
|
Chang CL, You C, Chen HM, Chiang CP, Chen CT, Wang CY. Autofluorescence lifetime measurement on oral carcinogenesis. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2004:2349-51. [PMID: 17270741 DOI: 10.1109/iembs.2004.1403681] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Normal and cancerous tissues have distinct autofluorescence lifetime because of their biophysical and biochemical differences. Protoporphyrin IX (PplX) is a useful fluorophore, which generally accumulates more in cancerous cells than in normal cells due to heme synthesis pathway, is often employed in photodynamic detection and therapy. Under 410nm excitation, the main emission peak of PplX is at 630nm. Autofluorescence lifetime at 630nm emission would be elongated if PplX gathered more in cells. In this study, we tried to find if there exist significant differences of autofluorescence lifetime at 630nm (under 410nm excitation) between normal and cancerous tissues for in vivo measurement. The result shows that normal tissues in general have shorter lifetime (about 2.8 approximately 3.5 ns) than that of abnormal tissues. The measured data suggest that lifetime would get longer in accordance with the degree of carcinogenesis. For cancer tissues, the average autofluorescence lifetime was extended to be about 10ns. Furthermore, the efficiency of treatment could also be defined refer to the time-series of lifetime decline.
Collapse
|
88
|
Okamoto J, Huang DJ, Mou CY, Chao KS, Lin HJ, Park S, Cheong SW, Chen CT. Symmetry of multiferroicity in a frustrated magnet TbMn2O5. PHYSICAL REVIEW LETTERS 2007; 98:157202. [PMID: 17501376 DOI: 10.1103/physrevlett.98.157202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2006] [Indexed: 05/15/2023]
Abstract
Based on measurements of soft-x-ray magnetic scattering and symmetry considerations, we demonstrate that the magnetoelectric effect in TbMn2O5 arises from an internal field determined by S-->q--> x S-->-q--> with S-->q--> being the magnetization at modulation vector q-->, whereas the magnetoelastic effect in the exchange energy governs the response to external electric fields. Our results set fundamental symmetry constraints on the microscopic mechanism of multiferroicity in frustrated magnets.
Collapse
|
89
|
Elfimov IS, Rusydi A, Csiszar SI, Hu Z, Hsieh HH, Lin HJ, Chen CT, Liang R, Sawatzky GA. Magnetizing oxides by substituting nitrogen for oxygen. PHYSICAL REVIEW LETTERS 2007; 98:137202. [PMID: 17501234 DOI: 10.1103/physrevlett.98.137202] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Indexed: 05/15/2023]
Abstract
We describe a possible pathway to new magnetic materials with no conventional magnetic elements present. The substitution of nitrogen for oxygen in simple nonmagnetic oxides leads to holes in N 2p states which form local magnetic moments. Because of the very large Hund's rule coupling of Nitrogen and O 2p electrons and the rather extended spatial extent of the wave functions these materials are predicted to be ferromagnetic metals or small band gap insulators. Experimental studies support the theoretical calculations with regard to the basic electronic structure and the formation of local magnetic moments. It remains to be seen if these materials are magnetically ordered and, if so, below what temperature.
Collapse
|
90
|
Fang CH, Chen YL, Yang CH, Chi Y, Yeh YS, Li EY, Cheng YM, Hsu CJ, Chou PT, Chen CT. Iridium(I) Pyridyl Azolate Complexes with Saturated Red Metal-to-Ligand Charge Transfer Phosphorescence; Fundamental and Potential Applications in Organic Light-Emitting Diodes. Chemistry 2007; 13:2686-94. [PMID: 17171730 DOI: 10.1002/chem.200601019] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Preparation of a new series of neutral metal complexes [(cod)Ir(fppz)] (1), [(cod)Ir(bppz)] (2), [(cod)Ir(fptz)] (3) and [(cod)Ir(bptz)] (4), bearing one cod ligand and a pyridyl azolate chelate are reported. A single-crystal X-ray diffraction study of 3 reveals the expected distorted square-planar geometry. The lowest absorption band consists of IrI atom increased triplet dpi-->pi* transitions (3MLCT), the assignment of which is firmly supported by the theoretical approaches. Complexes 1-4 exhibit weak phosphorescence in degassed solution at room temperature, whereas much more intense, solid-state phosphorescence appears in the range 622-649 nm. The pure MLCT emission was used as a prototypical model to address its remarkable spectral differences from the IrIII isoquinoline pyrrolide complex (5), which has mainly 3pipi phosphorescence. Complex 3 was used as a dopant to fabricate red-emitting phosphorescent organic light-emitting diodes (OLEDs). For the 7 % doped device, a maximum brightness of 3010 cd m-2 was achieved at an applied voltage of 15 V and with CIE coordinates of (0.56, 0.33), demonstrating for the first time the potential of neutral IrI complexes in OLED applications.
Collapse
|
91
|
Chen CG, Yang YL, Cheng HH, Su CL, Huang SF, Chen CT, Liu YT, Su IJ, Lo HJ. Non-lethal Candida albicans cph1/cph1 efg1/efg1 transcription factor mutant establishing restricted zone of infection in a mouse model of systemic infection. Int J Immunopathol Pharmacol 2006; 19:561-5. [PMID: 17026841 DOI: 10.1177/039463200601900312] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The cph1/cph1 efg1/efg1 Candida albicans mutant cells were non-lethal in a mouse model of systemic infection. We investigated in vivo proliferation and invasion of C. albicans cells in infected mice to elucidate the interaction between the host and the pathogen. Homogenates of kidneys from the mice infected with the wild-type and the mutant C. albicans cells yielded a mean of 2.1 x 10 7 CFU/g and 2.2 x 10 6 CFU/g, respectively. The kidneys from the mice infected with the wild-type cells showed extensive renal cortical necrosis associated with neutrophilic infiltration. There were also wild-type hyphal cells present in abundance. Hence, tubular necrosis leading to renal failure in the mice may be the cause of death. Although the cph1/cph1 efg1/efg1 mutant cells were not lethal, they were capable of establishing restricted zones of infection and colonization near the renal pelvis instead of simply being cleared by the immune system in mice.
Collapse
|
92
|
Haverkort MW, Hu Z, Cezar JC, Burnus T, Hartmann H, Reuther M, Zobel C, Lorenz T, Tanaka A, Brookes NB, Hsieh HH, Lin HJ, Chen CT, Tjeng LH. Spin state transition in LaCoO3 studied using soft x-ray absorption spectroscopy and magnetic circular dichroism. PHYSICAL REVIEW LETTERS 2006; 97:176405. [PMID: 17155490 DOI: 10.1103/physrevlett.97.176405] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Indexed: 05/12/2023]
Abstract
Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L(2,3) edge, we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply degenerate high-spin first excited state. From the temperature dependence of the spectral line shapes, we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low- or intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance, and inelastic neutron data.
Collapse
|
93
|
Cai YQ, Chow PC, Restrepo OD, Takano Y, Togano K, Kito H, Ishii H, Chen CC, Liang KS, Chen CT, Tsuda S, Shin S, Kao CC, Ku W, Eguiluz AG. Low-energy charge-density excitations in MgB2: Striking interplay between single-particle and collective behavior for large momenta. PHYSICAL REVIEW LETTERS 2006; 97:176402. [PMID: 17155487 DOI: 10.1103/physrevlett.97.176402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2006] [Indexed: 05/12/2023]
Abstract
A sharp feature in the charge-density excitation spectra of single-crystal MgB2, displaying a remarkable cosinelike, periodic energy dispersion with momentum transfer (q) along the c* axis, has been observed for the first time by high-resolution nonresonant inelastic x-ray scattering (NIXS). Time-dependent density-functional theory calculations show that the physics underlying the NIXS data is strong coupling between single-particle and collective degrees of freedom, mediated by large crystal local-field effects. As a result, the small-q collective mode residing in the single-particle excitation gap of the B pi bands reappears periodically in higher Brillouin zones. The NIXS data thus embody a novel signature of the layered electronic structure of MgB2.
Collapse
|
94
|
Chan LH, Lee YD, Chen CT. Achieving saturated red photoluminescence and electroluminescence with readily synthesized maleimide-arylamine copolymers. Tetrahedron 2006. [DOI: 10.1016/j.tet.2006.07.096] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
95
|
Koethe TC, Hu Z, Haverkort MW, Schüssler-Langeheine C, Venturini F, Brookes NB, Tjernberg O, Reichelt W, Hsieh HH, Lin HJ, Chen CT, Tjeng LH. Transfer of spectral weight and symmetry across the metal-insulator transition in VO(2). PHYSICAL REVIEW LETTERS 2006; 97:116402. [PMID: 17025910 DOI: 10.1103/physrevlett.97.116402] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Indexed: 05/12/2023]
Abstract
We present a detailed study of the valence and conduction bands of VO2 across the metal-insulator transition using bulk-sensitive photoelectron and O K x-ray absorption spectroscopies. We observe a giant transfer of spectral weight with distinct features that require an explanation which goes beyond the Peierls transition model as well as the standard single-band Hubbard model. Analysis of the symmetry and energies of the bands reveals the decisive role of the V 3d orbital degrees of freedom. Comparison to recent realistic many body calculations shows that much of the k dependence of the self-energy correction can be cast within a dimer model.
Collapse
|
96
|
Lee RH, Hsu HF, Chan LH, Chen CT. Synthesis and electroluminescence properties of a novel tetraphenylsilane–oxadiazole–diphenyl(para-tolyl)amine polymer. POLYMER 2006. [DOI: 10.1016/j.polymer.2006.07.074] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
97
|
Shih PI, Chiang CL, Dixit AK, Chen CK, Yuan MC, Lee RY, Chen CT, Diau EWG, Shu CF. Novel Carbazole/Fluorene Hybrids: Host Materials for Blue Phosphorescent OLEDs. Org Lett 2006; 8:2799-802. [PMID: 16774260 DOI: 10.1021/ol060884c] [Citation(s) in RCA: 170] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text] A series of carbazole/fluorene (CBZm-Fn) hybrids were effectively synthesized through Friedel-Crafts-type substitution of the carbazole rings. These compounds were thermally and morphologically stable host materials for OLED applications. Efficient blue phosphorescent OLEDs were obtained when employing CBZ1-F2 as the host and FIrpic as the guest.
Collapse
|
98
|
Chan LH, Lee YD, Chen CT. Synthesis and Characterization of 3,4-Diphenylmaleimide Copolymers That Exhibit Orange to Red Photoluminescence and Electroluminescence. Macromolecules 2006. [DOI: 10.1021/ma052083f] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
99
|
Huang DJ, Lin HJ, Okamoto J, Chao KS, Jeng HT, Guo GY, Hsu CH, Huang CM, Ling DC, Wu WB, Yang CS, Chen CT. Charge-orbital ordering and Verwey transition in magnetite measured by resonant soft X-ray scattering. PHYSICAL REVIEW LETTERS 2006; 96:096401. [PMID: 16606287 DOI: 10.1103/physrevlett.96.096401] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2005] [Indexed: 05/08/2023]
Abstract
We report experimental evidence for the charge-orbital ordering in magnetite below the Verwey transition temperature T(V). Measurements of O K-edge resonant x-ray scattering on magnetite reveal that the O 2p states in the vicinity of the Fermi level exhibit a charge-orbital ordering along the c axis with a spatial periodicity of the doubled lattice parameter of the undistorted cubic phase. Such a charge-orbital ordering vanishes abruptly above T(V) and exhibits a thermal hysteresis, correlating closely with the Verwey transition in magnetite.
Collapse
|
100
|
Eguchi R, Kiss T, Tsuda S, Shimojima T, Mizokami T, Yokoya T, Chainani A, Shin S, Inoue IH, Togashi T, Watanabe S, Zhang CQ, Chen CT, Arita M, Shimada K, Namatame H, Taniguchi M. Bulk- and surface-sensitive high-resolution photoemission study of two mott-hubbard systems: SrVO3 and CaVO3. PHYSICAL REVIEW LETTERS 2006; 96:076402. [PMID: 16606115 DOI: 10.1103/physrevlett.96.076402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2005] [Indexed: 05/08/2023]
Abstract
We study the electronic structure of Mott-Hubbard systems SrVO3 and CaVO3 with bulk and surface-sensitive high-resolution photoemission spectroscopy, using a vacuum ultraviolet laser, synchrotron radiation, and a discharge lamp (hv = 7-21 eV). A systematic suppression of the density of states (DOS) within approximately 0.2 eV of the Fermi level (EF) is found on decreasing photon energy, i.e., on increasing bulk sensitivity. The coherent band in SrVO3 and CaVO3 is shown to consist of surface and bulk-derived features, separated in energy. The stronger distortion on surface of CaVO3 compared to SrVO3 leads to a higher surface metallicity in the coherent DOS at EF, consistent with recent theory.
Collapse
|