High-resolution photoemission study of metallic, insulating, and superconducting BEDT-TTF salts

Journal Article · Wed Oct 01 04:00:00 EDT 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.56.9082· OSTI ID:632647

Sekiyama, A; Susaki, T; Fujimori, A ^[1]; Sasaki, T ^[2]; Toyota, N ^[3]; Kondo, T; Saito, G ^[4]; Tsunekawa, M; Iwasaki, T; Muro, T; Matsushita, T; Suga, S ^[5]; Ishii, H; Miyahara, T ^[6]

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1. Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113 (Japan)
2. Institute for Materials Research, Tohoku University, Aoba-ku, Sendai 980-77 (Japan)
3. Research Institute for Advanced Science and Technology, Osaka Prefecure University, Sakai 593 (Japan)
4. Department of Chemistry, Kyoto University, Sakyo-ku, Kyoto 606-01 (Japan)
5. Department of Material Physics, Osaka University, Toyonaka, Osaka 560 (Japan)
6. Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-03 (Japan)

We have made a high-resolution photoemission study of quasi-two-dimensional organic conductors BEDT-TTF salts which have various ground states, namely, antiferromagnetic insulator {kappa}-(ET-d{sub 8}){sub 2}Cu[N(CN){sub 2}]Clthinsp, paramagnetic metal {alpha}-(ET){sub 2}KHg(SCN){sub 4}, and superconductors {kappa}-(ET){sub 2}Cu(NCS){sub 2} and {kappa} -(ET){sub 2}Cu[N(CN){sub 2}]Br, where ET denotes BEDT-TTF or bisethylenedithio-tetrathiafulvalene. In all the spectra, the photoemission intensity is suppressed near the Fermi level (E{sub F}), especially for the {kappa}-phase salts, although we have clearly observed a finite E{sub F} intensity for {alpha}-(ET){sub 2}KHg(SCN){sub 4}. Hartree-Fock band-structure calculations for the paramagnetic metallic and antiferromagnetic insulating states qualitatively explain the spectra of {alpha}-(ET){sub 2}KHg(SCN){sub 4} and {kappa}-(ET-d{sub 8}){sub 2}Cu[N(CN){sub 2}]Cl, respectively, while those of {kappa}-(ET){sub 2}Cu(NCS){sub 2} and {kappa}-(ET){sub 2}Cu[N(CN){sub 2}]Br strongly deviate from the calculations for the corresponding ground states. These observations imply that, among the metallic compounds, electrons are more strongly correlated in the {kappa}-phase salts than in {alpha}-(ET){sub 2}KHg(SCN){sub 4}. It is shown that long-range electron correlation is quite important to explain the strong deviation of the spectra from the band-structure calculation. The spectra of the {kappa}-phase salts exhibit a remarkable similarity between the metallic (superconducting) and insulating phases across the chemical pressure-induced phase transition. We have also observed unusual temperature dependence of the spectra for {kappa}-(ET){sub 2}Cu(NCS){sub 2}, {alpha}-(ET){sub 2}KHg(SCN){sub 4}, and {kappa}-(ET-d{sub 8}){sub 2}Cu[N(CN){sub 2}]Cl. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 632647
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 14 Vol. 56; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANTIFERROMAGNETIC MATERIALS
ELECTRONIC STRUCTURE
FERMI LEVEL
GROUND STATES
ORGANIC COMPOUNDS
ORGANIC SUPERCONDUCTORS
PHOTOEMISSION